Replacing plywood transom?

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
I'm in the midst of a major makeover on a 24' 'toon. Everything going well, but I'd like some input on something. This boat is a '99, and although the plywood transom appears to be in OK shape, I'm re-powering from 40 hp to 90 (boat is rated for 140) so I'm planning on replacing it.

The question -
The transom appears to be laminated together from 2 pieces of 3/4" ply and 1 piece of 1/2". I have the 3/4" from cut outs in the new deck, and a piece of 1/2" from old furniture removed during the demo. So quality wood not an issue. The issue is what to use for glue? I'm thinking slow epoxy. Something that will not harden right away, allowing it to soak into the wood a bit prior to hardening. Thoughts?

Planning on using the front tire of my truck for a clamp. Just place the transom on the driveway and park the truck tire right on it for a day. That should provide plenty of clamping force.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
It won't make much of a difference in what glue you use, but it does need to be water proof. All the bolts, plus the motor mount bolts are through bolted, so the plywood doesn't really have anywhere to go.

​Don't park your truck on it, just clamp it lightly, too much clamping force will squeeze out all of the glue you used to put it together, resulting in a poor bond.
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
"ondarvr" has some great points above. As far as glue, a lot of iboater use Titebond III glue. It is totally waterproof and is easy to work with and still has a long enough working time to get everything adjusted as needed. And I would just use clamps as well so you keep the glue in the joint and not squeeze it all out like ondarvr stated. Glue is only as good as it can be if the glue is actually there in the joint. JMHO
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,307
I have about 6 containers of Titebond III around the house
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Can I assume that's what you would use in this application?
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
When I replaced my transom plywood, I glued the pieces together with Gorilla Glue polyurethane. It requires water to activate the glue and is waterproof. I picked it because I had some around the shop from other waterproof gluing jobs. So far, so good.
 

clemsonfor

Lieutenant Junior Grade
Joined
Sep 19, 2005
Messages
1,011
Is all your wood treated. I assume the deck ply is but what about the other?

That be my suggestions as well as just to use quality clamps. I prefer C clamps to the quick type.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Yes, all wood treated marine ply. I just finished this up today. I did use the Titebond, because it looked like it might be the easier approach. The original transom was used for a pattern, and as it was drilled for a motor already, I used it as a drill guide to drill holes in the new ransom (after confirming new engine was the same dimensions). I went over everything lightly with an DA sander using 80 grit to make sure everything was flat and to dress the corners a little. Everything was test fit, and after applying the glue, the layers were stacked on the motor mounting bolts that had been inserted through the first layer. This assured alignment, AND, when all was stacked and double checked again, I ran the nuts down on the bolts and just snugged them - providing even compression across the entire part. So nobody has to be concerned about me parking my truck on it....

Knowing full well how generous I had been applying the glue, I was surprised at how little glue oozed out actually. There's not a lot of doubt the wood soaked up much more than I thought it would.

All wiped down of the glue that did ooze out, new transom was test fit in U-channel on engine pod to confirm a near perfect fit. Now on to something else while that dries for a couple of days.....

Thanks for the thoughts guys. Much appreciated, resulting in a somewhat simpler process than I had planned on. -Al
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
ahicks, I see you stated that you used "treated plywood". Is this new transom going up against aluminum? If so, treat woods should never be used with aluminum. The chemicals they use to treat teh wood against rot, doesn't play well with aluminum and over a short period of time, will cause aluminum corrosion. You may want to look into that before installing it. Hate to be the bearer of such news, but I want your project to come out the best it can. JMHO
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
I did say that, but if you look above in the original post, you'll see the transom parts have been cut from the flooring project - the one using 100 dollar sheets of treated ply. I'm aware of the difference, but thanks for keeping your eyes open and the shout out. -Al

BTW, I did beat the 75 dollar "home delivery charge" on the plywood for my project by having the ply shipped to the local trucking terminal (Yellow Freight in this case). In such an arrangement, the terminal will call you telling you your shipment has arrived. At that point you hustle over to the terminal and they load the skid into the back of your pickup - free.
 
Top