Yanmar Builds Diesel Outboard to Accept Propeller Guard

Yanmar D27 & D36 Diesel Outboard Service Manual cover

Yanmar D27 & D36 Diesel Outboard Service Manual cover

Back in 2000, Yanmar was offering a special lower leg on Model D27A and D36A outboards (27 and 36 horsepower) that came with bolt holes for installing a propeller guard.

The boating industry has long claimed that all marine drive manufacturers are united in their stand against propeller guards. Drive manufacturers say their united stand is an example of how unsafe propeller guards are, the problems they create, and of the impossibility of designing a safe, functional propeller guard. Some marine drive manufacturers have voided the warranty of drives due to propeller guards being mounted on them.

Yanmar may not have installed them, but they set their drives up to use them. Yanmar Service Manual. Diesel Outboard Motor. Models D27A & D36A. Manual # A0A5055-JC03. Model Year 2000. The cover page, and page 141 are reproduced here.

It is obvious from these images that Yanmar built drives with the full intent of them being used with propeller guards AND did so at the request of their customers.

Yanmar Preforms Propeller Guard Mounting Holes

Yanmar preforms propeller guard mounting holes in diesel outboard lower legs

Those objecting to propeller guards sometimes claim the holes drilled for mounting some guards could cause the drive to corrode. Yanmar solved that problem by pre-forming the holes.

Others have claimed that outboards and stern drives were not designed to support propeller guards or the loads they might generate in use. Still others have claimed the drilling of mounting holes could weaken drives and cause them to break.

Long ago, we suggested marine drive manufacturers beef up the drives most likely to have guards mounted to them if necessary, and supply “knock-outs” that could be easily punched out to create mounting holes for propeller guards.

Propeller Guard Paradox Defeated by Ant Farm
Propeller Guard Information Center

“Drive manufacturers could design their drives in advance to accept their own propeller guards by beefing areas needing reinforced and by incorporating any necessary mounting holes either as pre-formed holes or as “knock outs” that could be easily removed.”

Yanmar took that approach one step further (even before we suggested the idea). They went ahead and drilled or formed the holes in an optional lower leg.


  1. I need the servie manual of Yanmar Diesel Outboard 27 & 36 HP and also the Parts Catalog!How may I find this books and how much they cost?

    I need to know the valve adjustment intake exhause
    and also information about the propeller guard (for 27 & 36 HP)

    Please I need this information ASAP

  2. We see a Yanmar diesel outboard service manual for sale on eBay as a CD. They may be authorized and real or they may not.

    Valve adjustment info may be in the service manual.

    Yanmar built an optional lower unit to accept a guard. We do not quickly see information of them selling a guard for it. I suspect some of the ring guards will fit that hole pattern as we have seen photos of Yanmar diesel outboards with ring guards on them.

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