Re: New to the site, questions about my first boat!
Welcome to iBoats!
If you click on my projects page below you will see a 15' tri hull that I'm doing the exact same thing to.
I haven't updated it yet, but I have removed to motor and got it ready for my 55 lbs electric troller.
What I did to seal the transom up was kind of a test of a product I'd never used.
I would go to walmart and look in the automotive section. Find Bondo brand epoxy. It is a 4 inch long piece of putty hanging up and it's dirt cheap. Get about four.
After you get the motor off, scrape all the silicone type adhesive away from the holes that go through the transom. Then drill the holes out with a half inch drill bit. This will acheive two things. It will clean up the holes to facilitate filling, and it will give you and idea of transom wood condition. Take a look at the wood shavings that come out - are they wet or totally rotten? If so, don't put another gas motor over 10HP on it.
Now you take the epoxy stick and cut off about an inch at a time. Knead it with your fingers very well for a minute and then push it into the holes. I didn't mix some of it well enough and it's a little soft. The directions say that once mixed, you only have two minutes to work with it so hurry! You need to reach both sides at once and compress it within the holes. Don't put too much in there. You want it slightly recessed into the holes, yet covering all the fiberglass.
The reason I say this, is because I let it form a mound outside the holes, and this stuff is rock hard. It just looks funny cosmetically. I suppose I could sand it but why waste the time and effort if you don't have to.
You can use marine tex (Ace hardware can order it), or 3M 4200 (walmart boating dept) to level the filled in motor mount holes and get a cleaner look.
I also did this with the speedometer pitot holes at the bottom of the transom, I just didn't have to drill all the way through obviously.
I also have some scrapes on the bottom of the hull that aren't too bad, but you can see fibers and I'm sure water will seep through slowly. I plan to marine tex them, but I haven't worked with marine tex yet, so we will see what happens.