Mounting an auxillary motor?

Posted September 13 2016

I'm bumbling my way through setting up an 18hp Tohatsu on an old Haines 565L. The main 125 Mercury has let me down a few times so I'd like to venture further offshore with more confidence.

I'm assuming a nylon base plate on the outside of the transom will be a good idea to secure the mount and damp vibrations. Can anyone please advise

A. If it would be okay to use a nylon cutting board, say 5mm thick, and

B. Whether I should also put a base plate under the inside lock nuts?

To complicate things, the top two bolts will have to go through the side of the built in bait box as well as the transom.

Thanks for any ideas!


3 people found this helpful. Do you?Thank Nick


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Posted September 13 2016
Hey Nick,

a. Polyethylene is what is normally used in about 6mm.

b. Yes, put a base plate so it spreads the stress / pressure across the fibreglass and acts as a washer.

If you're leaving it on permanently it's a good idea to fit with some some sikaflex to seal any water entry into the fibreglass/wood through the mounting bolt holes.

I don't know the exact setup but maybe an auxiliary mount would be suitable to possiblly to avoid the bait box?


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