Yamaha Possible Coverup of Propeller Guard Documents Exposed

Yamaha Prop Guard Statements

Yamaha Prop Guard Statements

In March 2012 Yamaha announced a new stainless steel propeller guard for outboards on flood rescue boats in the UK and made several statements about how great it was, how well it performed, and even how prop guards were necessary when people were in the water near the boat. About October we became aware of Yamaha’s new propeller guard. In mid October we began posting some materials about it and some of Yamaha’s own statements about their guard.

The boating industry has long defended itself in propeller injury court cases by claiming propeller guards don’t work. Among their objections, the industry claims guards create too much drag, reduce performance (top speed), effect the handling of the boat, are not durable enough, get bent into the propeller, and they create blunt trauma injuries when they strike people.

But Yamaha was making the exact opposite statements about their propeller guard. Yamaha said their guard worked great, minimized drag and performance reduction, improved handling, was strong and durable for use in shallow water, and guards were essential for operating rescue boats near people in the water.

Our mid October 2012 posts echoed several of Yamaha’s own comments.

By early November 2012, everything Yamaha ever said about the propeller guard AND all records of the guard’s existence vanished from their website. We made many attempts to contact Yamaha about why they pulled all of their materials about the propeller guard, but they will not respond. That leaves us to suspect Yamaha erased their statements to protect the boating industry’s long standing legal defense, “Guards don’t work”.

Among the many specific statements made and deleted by Yamaha about their propeller guard were: Read More →

Research Projects for Senior Design Classes, Masters Thesis Projects, Industrial Design & Other Researchers

Most college students in engineering and design take one or more design project classes, often a Senior Capstone Design Projects Class, in which they work individually or as teams to develop solutions to problems. We are trying to tap this resource and encourage students to consider selecting design projects related to propeller safety. More student design projects would help grow the body of knowledge available to the industry and to boaters. In addition to engineering and design students, we also welcome those from all fields and encourage them to consider projects in this area for their capstone classes. If you or others are interested in a college design class project or capstone project in propeller safety, propeller injury avoidance devices, or related fields, please view the projects listed below and contact us for additional assistance.

Propeller Guard

Propeller Guard

A few Masters and Doctoral students have written thesis and dissertations in this field. We strongly encourage Masters and Doctoral students looking for thesis and dissertation topics to contact us and discuss some of the possibilities available in their specific field of interest, as well as those looking for topics for scientific and technical papers.

We list of several possible boating propeller safety research projects below and will be posting more over time. Read More →

The Leash at the 2024 Bassmaster Classic on Grand Lake

We saw The Leash on several boats at the 2024 Bassmaster Classic on Grand Lake in Grove Oklahoma in March 2024.

The photos below show The Leash in action at the Bassmaster Classic.

Jamie Hartman

Jamie Hartman's Z21XL Pro Nitro with The Leash at the 2024 Bassmaster Classic

Jamie Hartman’s Z21XL Pro Nitro with The Leash at the 2024 Bassmaster Classic

Jamie Hartman was running The Leash on a Nitro Z21XL Pro powered by a Mercury outboard. He pulled out early Saturday.
His boat was parked in a great spot to capture some of the background, color, and spirit of the Classic.

Jamie Hartman's Z21XL Pro Nitro closeup with The Leash at the 2024 Bassmaster Classic

Jamie Hartman’s Z21XL Pro Nitro closeup with The Leash at the 2024 Bassmaster Classic

We also captured a nice closeup of The Leash on Hartman’s Nitro.

Brandon Card

Brandon Card running The Leash at 2024 Bassmaster Classic

Brandon Card running The Leash at 2024 Bassmaster Classic

Brandon Card was running The Leash on a Vexus Boat powered by a Suzuki outboard.

Josh Wiesner

Josh Wiesner running The Leash at 2024 Bassmaster Classic

Josh Wiesner running The Leash at 2024 Bassmaster Classic

Josh Wiesner from Wisconsin was running The Leash on a Ranger Z520 powered by a Mercury outboard.

Tim Tube

Tim Tube running The Leash at 2024 Bassmaster Classic

Tim Tube running The Leash at 2024 Bassmaster Classic

Tim Tube was running a Nitro boat powered by a Mercury outboard.

Tyler Williams

Tyler Williams running The Leash at 2024 Bassmaster Classic

Tyler Williams running The Leash at 2024 Bassmaster Classic

Tyler Williams was running a Skeeter boat powered by Yamaha.

Precision Sonar

Precision Sonar booth at 2024 Bassmaster Classic

Precision Sonar booth at 2024 Bassmaster Classic

Precision Sonar, marketing The Leash, displayed one an outboard in their booth. Lora is shown talking to one of their representatives. Precision Sonar’s booth was wide enough we had to cut the outboard out and move it over to the right in the image above.

A Recreational Boat

We came in a day early on Thursday and noticed a recreational boat in the parking area running The Leash.

The Leash on Recreational Boat at 2024 Bassmaster Classic

The Leash on Recreational Boat at 2024 Bassmaster Classic

This Nitro was powered by Mercury.

Jamie Hartman Video

After we returned back home, we found a Video of Jamie Hartman speaking about The Leash in Precision Sonar’s booth at the 2024 Classic.

About The Leash

The Leash has come a long ways since Chris Lane first ran The Leash at the 2016 Bassmaster Classic, also in Grove Oklahoma.

Precision Sonar reports The Leash continues to gain traction, particularly among bass anglers after major accidents.

Our previous coverage of The Leash includes:

Justin Hamner Wins 2024 Bassmaster Classic

We attended the 2024 Bassmaster Classic on Grand Lake in Grove, Oklahoma with the weigh-in and exhibition held in Tulsa.

The opening day blast off was a bit cool and damp on Friday March 22nd, but the large crowd was in great spirits as the anglers paraded by us on their way out of the great facilities at Wolf Creek Park.

While it was cool and damp, it was no where near as cold as it was at the 2016 Classic blast off at Wolf Creek.

The Winner

Justin Hamner, from Alabama, took home the coveted 2024 Bassmaster Classic Trophy with 58 pounds and 4 ounces over 3 days.

The image below is from Bassmaster’s coverage of the tournament.

Justin Hamner on stage at the 2024 Bassmaster Classic

Justin Hamner on stage at the 2024 Bassmaster Classic

Bassmaster also published some great images of his family, including his young daughter during the award of the trophy and the confetti that followed.

We took some nice photos of Hamner when he came in after day 2 on Grand Lake. The three images below are ours.

His Falcon Bass Boat was powered by a Yamaha Vmax SHO 250 horsepower outboard motor.

Justin Hamner rounding the corner on day 2 of the 2024 Bassmaster Classic preparing to trailer his boat.

Justin Hamner rounding the corner on day 2 of the 2024 Bassmaster Classic preparing to trailer his boat.

Read More →

Boating Safety Messages, Images, & Videos

We pulled a few basic boating safety materials together. We hope these images and videos will assist recreational boaters in becoming more prepared and to make safer choices.

Very basic boating safety points include:

  1. Take a Boating Safety Course
  2. Wear a life jacket when you are on the water
  3. Always attach your kill switch lanyard (engine cut-off switch / ECOS)
  4. Always kill the engine when near people in the water
  5. Never allow bow riding
  6. Be careful near marine life (sea turtles, manatees, dolphins, whales, and other marine life)
  7. Avoid the use of alcohol on the water
  8. U.S. Coast Guard provides boating safety resources at Recreational Boaters
  9. National Safe Boating Council (NSBC) provides numerous boating safety resources.
  10. Our YouTube playlist includes several Boat Propeller Safety videos
  11. covers boat propeller safety issues in great detail

View some online boating safety resources such as Yamaha’s Boating Safety Video by Hunter Bland.

Below are a few AI images we created promoting Boating Safety and Propeller Safety:

Mermaids in Life Jacket, Mermaids for Propeller Safety image

Mermaid in Life Jacket, Mermaids for Propeller Safety image

Life jacket and sea turtles for Propeller Safety image

Life Jacket and sea turtles for Propeller Safety image

Neon Mermaids for Propeller Safety image

Neon Mermaid for Propeller Safety image

Don't be the empty chair at your family's next holiday meal. Wear a life jacket.

“Empty chair” image resulting from the drowning of a family member. Wear your life jacket.

Updated our list of boats striking dredge pipes 2024

We updated our extensive List of Boats Striking Dredge Pipes on January 24, 2024.

Our list is now four pages long and includes about 175 individual dredge pipe strikes and mentions several more.

Dredge pipe strikes continue to claim lives as reported in Dredging Today as Boater Killed After Striking Dredge Pipe in Cape May Harbor.

In 2017 Mercury Marine made a presentation on the hazard of dredge pipe strikes to the Western Dredge Association which was discussed in the July/August 2017 issue of International Dredging Review. The cover page of Mercury’s presentation is shown below.

Mercury Marine 2017 presentation to Western Dredge Association on the hazards of dredge pipe strikes.

Mercury Marine 2017 presentation to Western Dredge Association on the hazards of dredge pipe strikes. Cover Page.

In 2015, the U.S. Coast Guard issued a Marine Safety Alert regarding the hazards of dredge pipes to boats. Click on the image below to see the full USCG Marine Safety Alert.

U.S. Coast Guard Marine Safety Alert regarding the hazards of dredging equipment. Heading of the document.

USCG Dredging Safety Alert title page.

Striking dredge pipes can cause those on board to be ejected and struck or repeatedly struck by the boat propeller as the unmanned boat circles. Striking dredge pipes can also result in the outboard motor breaking off and flipping into the boat still under power with the propeller turning a few thousand RPM.

Don’t make us add another page to our list of dredge pipe strikes, be very careful near dredging operations.

Expose on boat propeller accident propels Arizona to action

Every weekend on Lake Pleasant led to a major boating accident for several weeks this summer (2023). Some of these Maracopa County, Arizona accident were boat propeller strikes.

A local media outlet, Arizona’s Family released a great video on November 15th, 2023. The video uses one boat propeller accident as an introduction to talking more broadly about the problem. The video also addresses issues specifically associated with rental boats which are more frequently involved in propeller accidents.

Arizona Family’s report states, “In Arizona, two people died from prop strikes and 60 people suffered boating injuries.”

The YouTube video below issued November 15th.

The video was introduced by print media as Propeller strikes maim or kill recreational Arizona boaters every year.

This video is not just a video to watch and move on. It is a video to propel people to action. Some will take a boating safety class. Viewers will be more aware of their surroundings on a boat. Some rental boat agencies may re-evaluate their training process. Others will share the video with their friends and colleagues.

The Padilla Accident

The video specifically follows the July 22, 2022 incident in which 34 year old Alyssa Padilla was struck by a boat propeller.

Per the video, first responders were about 30 minutes getting to her. Response is often slow on large western lakes due to distance. They also often face difficulty locating novice rental boaters on large lakes.

Once on shore and stabilized she was taken by golf cart to an ambulance, then to a life flight helicopter.

Alyssa speaks out about her life changing injury and notes, “I will never be the same.”

Per the video, Alyssa later learned what happened to her happens a lot here and at other lakes.

Propeller Accident Statistics

The reported notes another woman died last summer. A six year old girl died this year. Both died by propeller strikes on Lake Pleasant.

The reporter states the U.S. Coast Guard reported 173 propeller accidents last year.

The Danger of Boat Propellers

Arizona Family’s reporter went on to say every single one of them was preventable.

Maricopa County Sheriff’s Deputy Detective Rob Marsky officer says the first thing you will hear is, “It happened so fast.”

He noted “propellers are like blenders”. “Even at idle speed a propeller could spin 40 times a second.”

Deputy Marsky stated,”Our victims can bleed out very, very quickly.”

Common Boat Propeller Accident Scenarios

“The number one reason that prop strikes happen is because of operator inattention.”

“One of the most common scenarios is someone is behind the boat, goes to swim toward the boat, and the driver turns the motor on.”

The article points out the boat ladder is often attached to the back of the boat right next to the motor and propeller.

Alyssa Padilla explains that when the boat was started, it created a suction of water into the propeller which was taking her into the propeller.

Propeller Safety Issues Concerning Rental Boats

Joe Watkins represents Alyssa in a lawsuit against Scorpion Bay, the firm that rented the boat. Mr. Watkins says propeller strikes do happen on really disturbing regular basis. He goes on to note they tend to happen to people that are renting boats.

The video goes on to discuss safety briefing issues involving rental boats.

In Alyssa’s instance, the sheriff’s office says the boat rental company did not even have the name of the person that rented the boat.

Deputy Marsky recounts the importance of boat operators receiving boating safety education.

Arizona is one of four states with no requirements for boat operators to receive safety training.

Our Comments

We salute Arizona Family, Alyssa Padilla, Officer Marsky, Joe Watkins, and their production crew. Their work will increase awareness of boat propeller accidents. They also exposed safety issues at some boat rental facilities.

While we can’t thank them enough, we do take issue with three points made in the video:

Point #1. 173 accidents reported by USCG in 2022

The video states, “Last year (2022) across the country the U.S. Coast Guard reported 173 accidents where people were struck by boat propellers.”

They are correct, in 2022 USCG reported 173 incidents in which one or more people were struck by a boat propeller. However, the actual total of individuals struck by a boat propeller reported by USCG in 2022 was 182 injured and 41 fatalities.

In addition, there has long been a tug of war over propeller strike statistics. The boating industry claims almost all propeller injuries are reported and propeller safety advocates argue many propeller accidents are not reported.

Note – the second print version of the article did include the statistics provided above. They were likely left out of the video to shorten it.

Point #2. Even at idle propellers can be rotating at 40 times per second

If an outboard powered boat was idling at 1,000 RPM in gear with a 2 to 1 reduction in the gearcase, the propeller would be turning about 1,000 RPM / 2 = 500 RPM or 8.3 times per second.

Several propeller safety brochures note the number of blades on the propeller is also important. For example even at 8.3 revolutions per second, a three bladed propeller could strike you 25 times per second.

The old U.S. Coast Guard “Beware of Boat Propellers…A Hidden Danger” brochure stated,”A typical three-blade propeller running at 3,200 rpm can inflict 160 impacts in one second.”

Cropped from the U.S. Coast Guard 2007 flyer, "Beware Propellers...A Hidden Danger".

Cropped from the U.S. Coast Guard 2007 flyer, “Beware Propellers…A Hidden Danger”.

Point 3. The reporter said, “Every single one of them was preventable.”

We agree many propeller accidents are preventable or at least can be mitigated. Tools currently available include boating safety education, rental boat safety training, operator attention, use of a spotter, sober boat operator, avoiding or limiting alcohol consumption by all on board, no use of drugs, not going faster than conditions allow, always having a lookout, and keeping your boat in proper condition.

Other existing prevention and mitigation methods include having proper safety equipment onboard, wearing a life jacket, using a kill switch / ECOS lanyard, first aid kits, no bow riding, divers and snorkelers always using dive flags, boat safety inspections, keeping a spare lanyard for use if the operator is ejected, etc. While this is just a partial list, it is easy to see why novice boaters might not cover all these bases, especially in a party environment on a lake they are no familiar with.

Point 3 Part A

Other propeller accidents could be prevented or mitigated with the use of additional safety equipment often not found on board such as VHF radios, GPS, first aid kits on rental boats, tourniquets or something that could be repurposed as a tourniquet on rental boats, indicators showing those in the water when the engine is running and the propeller is turning.

Another safety tool useful on large lakes is an Emergency Position Indicating Radio Beacon (EPIRB).

Point 3 Part B

Still more propeller accidents could be prevented or mitigated by design or equipment not accepted by boating industry manufacturers. Examples include boat propeller guards on slow moving rental boats, increasing distance from the ladder to the propeller, rear view cameras like on cars, removing the front ledge of pontoon boats that attracts bow riders at least on rental boats, using a doorbell switch to force the use of a spotter at the rear of a houseboat while backing up.

Additional designs and equipment not accepted by the boating industry include auto detection and stopping of circling unmanned boats, use of two stage tilt cylinders, use of products of the nature of The Leash”, devices only allowing certain users to pilot rental boats, use of warnings that point out the result if you do not follow them, and Public Service Announcements that graphically illustrate what can happen to you.

Even if most of the protections mentioned above were in place, boat propeller accidents will still occur. Challenges that can place someone in contact with a propeller include severe weather, mechanical failures, kill switch failures, steering failures, medical emergencies, striking submerged objects, hitting a stump, striking a dredge pipe, hitting a rock, becoming grounded and trying to push the boat off a sandbar, becoming entangled in a tow rope, horseplay.

Additional ways propeller accidents will still occur include boater fatigue, wakes generated by large vessels nearby, rogue waves, running over a diver or snorkeler without a dive flag, people swimming in open water, people swimming outside of a swim area, boats capsizing or sinking, other boats running over your boat, solar glare, changing lake levels, and mixed traffic (canoes, kayaks, paddle boards) with larger faster vessels.

And there are multiple paths by which those onboard PWC’s can contact your boat’s propeller.

For a More Complete List of Boat Propeller Accident Scenarios

See our propeller strike scenarios list for a more complete listing.

In Closing

Thanks again to ArizonaFamily for this important video. We hope many people and businesses will be inspired to take action based upon this video. They have a vastly larger and broader audience than us. We thank them for their efforts.

Mercury Pro XS Fatal Flaw video: flipping into boat

“MERCURY PRO XS FATAL FLAW! ARE YOU AT RISK?” video was released on YouTube October 28, 2023.

The video was produced by Team Marine Service, a La Crosse, Wisconsin based marine service & repair business.

It focuses on recently manufactured Mercury Marine Pro XS outboard motors breaking off and flipping into boats.

Andy Houser of TMS discusses several recent accidents in which large Mercury outboard motors broke off and flipped into boats.


The video notes many of the Pro XS outboard motors have broken in exactly the same spot (the swivel bracket).

He appeals to Mercury to let him visit the plant for a sit down visit with them. He would like to be able to ask them, Why is this breaking?”

Suzuki and Yamaha have recently sent representatives to visit with him in La Crosse.

Houser notes the video is not an attack on Mercury. They just want Mercury to recognize the problem, fix it, and let the public know what they need to do to stay safe in their boat.

Houser recognizes outboard motors are abused. He notes that for those running nearby in the Mississippi River “its like a war zone out there.” People hit stuff all the time.

He presents “The Leash” as a means to stay safer at this time.

In efforts to keep his viewers safe, Houser said, “If you are running a Mercury, go get a Leash for me.”

Our Comments

Team Marine Service seems to think this is a recent problem with Mercury Pro XS outboard motors. Our list of large outboard motors breaking off and flipping into boats and our list of all sizes of outboard motors breaking off and flipping into boats show the problem goes back decades.

We previously produced two volumes of methods to prevent or mitigate this problem. Many of them already patented, but not used, by the boating industry.

  1. Approaches to Prevent Outboard Motors From Flipping Into Boats After Striking Floating or Submerged Objects Third edition. 2018.
  2. Approaches to Prevent Outboard Motors From Flipping Into Boats After Striking Floating or Submerged Objects Supplement #1. 7 November 2020.

We also produced:

In closing, a big thanks to Andy Houser and his team at Team Marine Service. Their video will increase awareness of the issue and help save lives.

Monitoring outboard log strikes: Yamaha Patent Application

Yamaha’s U.S. patent application, “Collision Information Providing System, Collision Judging System, and Marine Vessel” was published October 12, 2023.

Yamaha’s system classifies and monitors three different kinds of collisions.

1. Outboard motor / Marine drive collisions

2. Propeller collisions

3. Vessel collisions

These types of collisions are monitored. They are classified. Their intensity is rated. Additional data is recorded.

Collisions are classified by type: marine drive, propeller or vessel collision. (ECU) Engine Control Unit data is monitored and used in the decision making. ECU data used includes engine rpm, throttle setting, air intake pressure, trim position, and shift status (forward, neutral, reverse). The ECU also reports if the shift mechanism is in the process of shifting.

Yamaha refers to struck a log / log strike as a driftwood hit.

Yamaha’s Patent Application

A full copy of Yamaha’s patent application can be found on Google Patents.

The front page of Yamaha’s U.S. Patent Application 2023/0322341 A1 is shown below.

Yamaha log strike monitoring patent application page 1

Yamaha log strike monitoring patent application

Yamaha notes their system applies to all types of marine drives. They specifically list jet boats outboard motors, inboard motors, and inboard outboard motors (stern drives).

Detecting and Classifying the Collision

The first step is detecting a collision by monitoring numerous data sources.

The next step is classifying the collision as being a vessel collision, propeller collision, or driftwood hit (log strike). Unrelated events such as jumping a wake are screened out during the classification process.

Yamaha uses the process outlined in Figure 4 below to classify collisions.

Yamaha outboard motor / marine drive collision monitoring patent application Figure 4: Collision Judging Process

Yamaha outboard motor / marine drive collision monitoring patent application Figure 4: Collision Judging Process

The classification process is described in much greater detail in the patent application. The patent application notes the importance of rejecting other events that might register as a collision. Several such events are listed below.

1. Intentional sudden acceleration of the boat
2. Intentional sudden deceleration of the boat
3. Jumping a wave
4. Engine Cut-Off System (ECOS) / Kill Switch activation
5. Recognizing a propeller has multiple blades and may strike the same object multiple times during a single collision
6. Engine RPM is not stable for a period of time after the engine is started.
7. Intentional throttle position change
8. Low speed and low intensity collisions

Examples of the Classification Process

Some Indicators of a Marine Vessel Hit:

A data table of g acceleration values vs. vessel speed is one of the variables to determine if their was a marine vessel hit.

For example, a value of 1g at speeds of 10 kph or less is an indication a marine vessel hit.

While a value of 24 or more g at speeds of 40 kph or more is an indication a marine vessel hit.

Some Indicators of a Driftwood Hit / Log Strike:

  • Speed must equal or exceed 10 kph.
  • Inclination angle must change by more than 10 percent of the total trim range within 100 ms.
  • After the strike, inclination angle must exceed 120 percent of total trim range within one second.
  • After the event, the drive settles back down.
  • An acceleration sensor on the outboard may directly measure rotational acceleration of the drive.

  • Additional Impact Data Sensors & Sources

    Additional data used in the decision process may include:

    1. Rate of Change of Engine RPM
    2. Video from the time of the incident
    3. Maximum tilt of the drive after the log strike
    4. How fast the drive was tilting
    5. Angular acceleration of the drive from an accelerometer
    6. Status of steering (was the boat in a turn
    7. Marine vessel speed sensor reports speed<"/li">
    8. Engine RPM may be used to estimate speed
    9. GPS location dataGPS may be used to determine boat speed.
    10. Direction of travel of the boat (is it going forward or backward)
    11. Temperature of Engine Cylinder Wall (indication of recent startup)
    12. Audio – sounds including voices on and around the boat at time of collision
    13. Weather

    Missing From the Patent Application

    Noticeably absent from the list of variables is hydraulic tilt cylinder pressure which has been used by others to determine intensity of log strikes.

    Also absent was detecting a quick turn which was suggested by Honda as a means of detecting a near impact. Quick turns in conjunction with some of the other variables may improve impact classification.

    The patent application does not specifically use the phrase “sensor fusion”. However, they do describe using multiple sensors to make a judgement if a collision occurred and what type of collision it was when not all sensors indicate the same result or some sensors may not be present.

    Data Recording and Storage

    Yamaha’s collision judging system stores data. The data is over written every few minutes unless there is a collision. If there is a collision, the collision is classified, and intensity of the collision is judged. Data surrounding the time before and just after the collision is permanently stored and/or transmitted to a remote site.

    Yamaha suggested video could be saved from 30 seconds before the accident through 5 seconds after the accident.

    Boat Rental Applications

    Yamaha’s patent mentions their collision monitoring device has special application to the boat rental market. Marinas could check the system for any impacts when the boat comes back in after a rental. The system could wirelessly report to the marina. In addition, Yamaha’s collision system can estimate damage to the propeller after a collision.

    Similarly, the system could be used by individuals who loan out or charter their boat. When the boat comes back they can check it’s status. They could even monitor their boat in real time.

    While not specifically mentioned, they system could also be applicable to larger sailboats.

    Outboard motor / marine drive collisions

    Outboard motor trim and tilt ranges

    Outboard motor trim and tilt ranges

    The system appears to classify medium intensity log strikes as opposed to catastrophic log strikes. Their highest impact rating goes is awarded when the drive flips up an additional 120 percent of the normal trim range. As we understand it, that means a flip up of 120 percent of 15 degrees in addition to the trim at time of impact. If the drive was trimmed up 7 degrees, their highest impact rating would be given for the drive flipping up another 1.2 X 15 degrees. Or reaching a trim/tilt of a total of 7 degrees plus 18 degrees = 25 degrees.

    Catastrophic strikes bring the outboard on up toward maximum tilt. In some instances outboard motors can break off after maximum tilt and flip into the boat. The engine may still be running as is the propeller.

    Some drives break off before the drive clears the object. In that event, the failure would be obvious and would not need to be recorded.

    Marine drives that are unable to clear the object or take an abnormal time to clear the object might not be classified as driftwood hits.

    Judging Driftwood Hits / Log Strikes

    Yamaha reveals a system in Figure 5 in which they use the rate of change of trim, along with the maximum change in trim/tilt to judge or rate the intensity of a log strike.

    Yamaha outboard motor / marine drive impact intensity scoring system

    Yamaha outboard motor / marine drive impact intensity scoring system

    System Cost

    The full system could require additional sensors, computing power, and a data storage system.

    Yamaha notes “All of the data used in the above-described detection of the occurrence of the propeller hit performed by the ECU is able to be obtained by the existing sensors, etc. of the outboard motor. Therefore it is not necessary to add any additional sensors, etc. in order to perform the detection of the occurrence of the propeller hit, and it is possible to suppress the cost.”

    While Yamaha does not mention it, this system could also be useful in detecting and recording human propeller strikes. One problem however, could be some propeller accidents occur shortly after the engine is started. Yamaha’s system does not detect propeller strikes till the engine cylinder walls warm up and engine RPM becomes more stable.


    Patentability is determined by patent examiners at the U.S. Patent Office. Several systems in this category (monitoring / recording log strikes) have already shown up in the patent system. We even suggested one ourselves.

    We note Yamaha cites two of their previous Japanese Patents related to this invention. Thus, we may see one or more additional U.S. Patent Applications related to this device. Sometimes manufacturers use one patent to protect the methods used by the device and another patent to protect the device itself.

    Related patents and inventions include

    • Suzuki Japanese Patent JP5810881 (B2) – 2015-11-11. “Device, Method and Program for Controlling Collision of Outboard Motor”. Suzuki records tilt vs rate of change of tilt during impacts. See Approaches to Prevent Outboard Motors From Flipping Into Boats pages 167-169. Note the invention is incorrectly attributed to Yamaha in that publication. It is a Suzuki invention.

    • Brunswick: Brunswick filed separate system and method patents for detecting and recording marine drive impacts including their severity. Both patents determine an underwater impact occurred and its severity by monitoring the rate of change of trim and comparing rate of change to a stored value. See Approaches to Prevent Outboard Motors From Flipping Into Boats: Supplement 1 pages 52-54.
      1. U.S. Patent 10,214,271 Systems and Methods for Monitoring Underwater Impacts to Marine Propulsion Devices. Issued 26 February 2019. This patent has the METHOD claims.
      2. U.S. Patent 10,577,068 Systems and Methods for Monitoring Underwater Impacts to Marine Propulsion Devices. Issued 3 March 2020. This patent has the SYSTEM claims.

    • Honda was issued two patents for a marine drive impact recording system. See Approaches to Prevent Outboard Motors From Flipping Into Boats: Supplement 1 pages 57-60.
      1. U.S. Patent 10,272,977 Boat Navigation Assist System, and Navigation Assist Apparatus and Server of the System. Issued 30 April 2019.
      2. U.S. Patent 10,746,552 Boat Navigation Assist System, and Navigation Assist Apparatus and Server of the System. Issued 18 August 2020.

    The Leash Saves Bass Angler From Outboard Motor

    A bass angler was fishing on Santee Cooper Lake in South Carolina. His Mercury Pro XS outboard motor struck a floating log at about 55 miles per hour.

    The outboard motor broke off at the swivel bracket during the October 2023 accident. Several large Mercury outboard motor swivel brackets have failed, allowing the outboard to flip into the boat.

    The Leash is available from Precision Sonar. The Leash prevented this bass fisherman’s Mercury outboard from entering his Ranger boat and killing or maiming him.

    Mercury Marine Pro XS outboard motor broke off Ranger boat and was restrained from flipping into the boat by The Leash

    Mercury Marine Pro XS outboard motor broke off Ranger boat and was restrained from flipping into the boat by The Leash

    This swivel bracket broke horizontally across the top near the serial number tag, as seen below.
    The Leash is in the lower part of the image. Part of The Leash’s cover came off during the accident (see the brown rope-like color).

    Mercury Marine Pro XS outboard motor swivel bracket broke in Santee Cooper log strike

    Mercury Marine Pro XS outboard motor swivel bracket broke in Santee Cooper log strike

    This bass fisherman used his trolling motor to get back to the boat landing and lived to fish another day.

    See this Precision Sonar Facebook post for additional photos and details on this accident.

    More Information on The Leash

    More information and several great photos are available from Precision Sonar’s Facebook Page.

    The image below shows two Mercury outboards with The Leash installed. Other methods of installation are now available.

    The Leash: left and right views side by side

    The Leash: left and right views side by side

    Rex Chambers and his fishing partner were injured in 2014 when they struck a submerged log. The 250 horsepower Mercury outboard motor broke off, and flipped into the boat still under power.

    Rex later posted a video on his Facebook page about The Leash.

    We liked his down home, straight forward talk and how he is able to speak from personal experience of the need to tether large outboard motors. He has since passed on, but was and continues to be bass fishing great.

    Honda Air Bag Propeller Guard Patent Application

    Honda Motor Co of Japan filed a U.S. patent application for a propeller guard partially consisting of an air bag
    The patent application, US 2023/0278686 A1 “Outboard Motor Control Apparatus and Control Method for Outboard Motor” was published by the U.S. Patent and Trademark Office on September 7, 2023.

    Honda’s patent application has to do with preventing propeller contact with objects or people behind the vessel. It also focuses on preventing objects from winding up on the propeller. This post will focus on Honda’s efforts to prevent people from being stuck by a propeller while behind a boat.

    An image of the device is shown below:

    Honda air bag propeller guard patent drawing

    Honda air bag propeller guard patent drawing

    The device consists of a soft, elastic rearward protrusion from the propeller containing an airbag.

    How Honda’s Airbag Propeller Guard Works

    First, please note Honda does not refer to this invention as a propeller guard. They call it an “Outboard Motor Control Apparatus and Control Method for Outboard Motor”.

    If someone contacts the soft, elastic protrusion behind the propeller, it mitigates their impact. Then the resistance to rotation begins to slow the rotational speed of the propeller. Or, it begins to slow the acceleration of the rotational speed of the propeller. Thresholds are determined and programed into the Engine Control Unit (ECU). This slowing or rate of slowing can also be used to determine if it is a person or not. The system can affirm a person is there via infrared sensors or a camera.

    An alarm can be sounded depending on what is in contact with the protrusion behind the propeller.

    If it is a human, priority can be assigned to this finding. Propeller rotation can be quickly stopped and an air bag can be inflated to push the human away from the propeller.

    The air bag can also slow the human down if they were rapidly approaching the propeller.

    The Diagram below shows how the system basically works.
    Note the power system is referred to as “the prime mover” leaving room to cover fossil fuel engines, battery powered outboards, or other prime movers.

    Honda air bag propeller guard diagram patent drawing

    Honda air bag propeller guard diagram patent drawing

    The Logic System

    The basic logic used by the ECU to make decisions surrounding this propeller guard or virtual propeller guard is shown below.

    Honda air bag propeller guard logic map patent drawing

    Honda air bag propeller guard logic map patent drawing

    Other Features

    The patent application speaks of urgently stopping the rotation of the propeller. However it does not elaborate on how that will be done.

    The soft, elastic protrusion containing the airbag can be detached from the propeller. This makes it easily installable for specific applications. No specific applications are listed. Some potential outboard powered boat applications that come to mind are:

    • skiing and tubing
    • rental houseboats
    • rental pontoon boats
    • dive boats
    • boats used in “raft ups”
    • youth sailing coach boats
    • rescue boats and flood rescue boats
    • Some might suggest their use on outboard motor powered boats during wake surfing. That is a debate for another time
    • military applications
    • protecting commercial diver airlines from the propeller
    • military minesweeper arrays on the surface of the water, towed by helicopters use very expensive cables that might be protected by this device

    Even More Features

    Honda’s patent application describes an emergency button on the outboard motor at a location that could be triggered by swimmers that feel they are in danger.

    Most outboard motors are used with through prop exhaust. This patent application does not explain the details of that feature.
    There may be additional patent applications coming with greater details on certain elements of this invention.

    Automotive airbags and refilling them can be very expensive. Many boaters are used to more economical cartridges used to inflate life jackets. No mention is made of the cost of Honda’s approach.

    The system is adaptable to boats powered by multiple outboard motors.

    Mechanics of Filing This Patent Application

    Honda Motor first filed a patent application in Japan on December 28, 2021.

    Almost a year later, they filed the U.S. patent application on December 13, 2022.

    The U.S. Patent Application was published September 7, 2023.

    Our Comments

    We salute Honda Motor for thinking outside of the box and placing one more approach to boat propeller safety in the literature.

    We hope Honda is able to bring this device to market and generate more interest in this field.

    Malibu Boats Safety Alert: Bow Seating Hazard

    Malibu Boats released a Safety Alert regarding a Bow Seating Hazard on July 18, 2023.

    Malibu reports the safety alert is due to a tragic incident that occurred with a Malibu Response LX boat. A passenger was washed out of the bow seating during a bow swamping incident. The passenger was then hit by the propeller and died.

    2000 Malibu Response LX Courtesy

    2000 Malibu Response LX

    To prevent this from occurring again, Malibu now prohibits passengers in the bow of similar boats, while the boat is in motion. They will provide updated capacity labels and warning stickers reflecting this new safety policy.

    The Safety Alert identifies specific Sunsetter, Mystere, Echelon, Response, and Sportster models and years subject to this change.

    Malibu Boats notes their commitment to safety. “We sincerely regret that a Malibu branded boat was involved in such a tragic accident. Malibu is committed to the continuous improvement and safety of watercraft.”

    In closing Malibu notes they understand reducing your boat’s seating capacity is an inconvenience, and apologizes for doing so.

    The Safety Alert

    Malibu’s Safety Alert is available in pdf format from a link at the top of this post. The Safety Alert is also available in the images below:

    Malibu Boats Safety Alert: Bow Seating Hazard Page 1

    Malibu Boats Safety Alert: Bow Seating Hazard Page 1

    Malibu Boats Safety Alert: Bow Seating Hazard Page 2

    Malibu Boats Safety Alert: Bow Seating Hazard Page 2

    Malibu Boats Safety Alert: Bow Seating Hazard Page 3

    Malibu Boats Safety Alert: Bow Seating Hazard Page 3

    Malibu Boats Dealer Version of the Safety Alert

    As is often done in situations like this, Malibu prepared a Service Advisory version of the Safety Alert specifically for their dealers. The Dealer Service Advisory conveys similar information in abbreviated form. It also tells them to provide the following instruction to owners of these specific boats. “DO NOT allow passengers in the bow area while in motion.”

    Malibu Boats Dealer Service Advisory

    Malibu Boats Dealer Service Advisory: Bow Seating Hazard

    Our Comments on Malibu’s Safety Alert

    We posted our comments on Malibu’s Safety Alert on a separate post, Comments on Malibu Boats Safety Alert : Bow Seating.