Design Chart for Preventing Outboard Motors From Entering Boats

We charted the the Design Flow Process designing outboard motors in a manner that prevents them from entering the boat after striking submerged objects. The chart was designed specifically with tournament bass boat outboard motors in mind.

The chart has since been updated since it was originally posted. The most recent version is below.

Flip In Design Chart

Flip In Design Chart

Click on the chart above to view a larger pdf version of the chart.

As seen from the chart above, the process is quite basic. You need to:

  • Design the outboard to not break off when striking fixed submerged objects up to the highest speed practically possible (which may be less than the top speed of the vessel, unless you allow the lower unit to shear off). Many existing and potential methods to increase “Y” (speed at which it breaks off) are presented in Approaches to Prevent Outboard Motors From Flipping Into Boats After Striking Floating or Submerged Objects
  • Limit/reduce maximum speed of the vessel (outboard motor). For example, tournament bass boats are currently limited to 250 horsepower. Personal watercraft are currently limited to 65 mph plus a 2mph leeway in the United States.
  • Use a tether to prevent any outboard motor that may break off at higher speed collisions with fixed objects from entering the passenger area of the vessel.
  • Fail-safe test the system, including the transom and any jack plates approved for use with the outboard.


As shown in the chart, warnings are an option, but they will not be effective in preventing all outboard motor broke off and flipped into boat accidents. Many submerged objects are invisible to the boat operator, or invisible until it is too late to miss striking them. At least some of these invisible objects are randomly distributed.

Also not prevented are those in which the operator failed to see, read, understand, remember, or follow the warnings.


  1. It’s really interesting to see the thought process that goes into designing an outboard motor. They really consider things that the average person would never think of. I would never have thought of the risk of the motor ending up in the boat in the event of an accident. It’s probably thanks to careful planning like this that I have never heard about this before! Keep up the great work!

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