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Thread: outboard motor on o'day 27' - transom strength? Reply to Thread
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  Topic Review (Newest First)
11-18-2010 08:06 AM
sailingdog whatever you do, spread the load over as large an area as possible. Don't forget to encapsulate the plywood in fiberglass, or at least epoxy saturate it. Also, don't forget to pot the holes going through it.
11-18-2010 07:33 AM
imagine2frolic I really like the idea of using thinner ply, and adding to it if the stern is not flat, and the larger the better.........i2f
11-17-2010 11:29 PM
ccollins0601 The flex you are seeing is surprising. I have an O'Day 27 (1973) with a 12hp outboard. I have never seen any flex or weakness in the transom, and even use it as a step to get up on the boat sometimes when it's on the hard. I don't specifically remember what (if any) size of backing plate is used, the transom is so sturdy that it has been a long time since I looked.

One caveat: my boat was built as an outboard model (never had an inboard) so it may have different construction than the models with inboards.
11-16-2010 05:33 PM
Originally Posted by seamoosecap View Post
do you think epoxying some marine plywood to the inside over a large area (3'x3') would do it?
That should help. It would be best if your plywood extended
the entire height of the transom, and was tabbed with fiberglass
at top and bottom. That will transfer some of the loading
to the hull and deck structure.
That is quite a large motor for a ODay 27,
and I think you want to eliminate any flex that
might eventually fatigue the laminate.
11-16-2010 05:27 PM
Another Oday w/outboard

I have a '79 O'Day 28. The saildrive was pulled by a prior owner who installed an outboard hydraulic assist bracket rated for 15hp. It holds a 9.9hp Mariner that weights 86lb. I've had it on and off several times. This transom doesn't flex at all. This mount is backed by a couple circular plywood plates that are very thick. I've never measured them but it wouldn't surprise me if they we 3/4." The transom is also a reverse angle. Flexing would bother me. Good luck.
11-16-2010 05:14 PM
deniseO30 I forget, but it was pretty large . Plywood make more sense though.
11-16-2010 05:01 PM
seamoosecap denise,

how big (area) was the 1/4" aluminum plate on your hunter 23?

11-16-2010 02:28 PM
deniseO30 3/4 or double would work. the hard part is getting it pressed up tight. you could use 1/4" and press it into the back of the transom then and another.. then another, that way you could meet the curvature of the transom.
11-16-2010 02:23 PM
seamoosecap do you think epoxying some marine plywood to the inside over a large area (3'x3') would do it?
11-16-2010 11:25 AM
tommays Its going to stress and fatigue the glass if you can see it moving

I have seen many boats with custom wood (or what ever) part made on the outside to help spread the load over a larger area
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