transom replacment and rivet advice wanted.

I'm going to be replacing the transom on my 1542 Monark and just want to make sure I'm going about it the right way. there is a bulk head that I need to remove to get at the transom. the bulk head has some large rivets and a small weld holding it in place.

first question is where can I find the large rivets in the photo or can I use some regular popgun rivets here?

there is also a small weld in the corner that I assume I'll have to cut off. do you think I can put it back together without welding it or could i use some rivets instead? I'm guessing that I'll just have to use my judgment once I have it back together and feel how solid it is.

final question is what are some good options for transom material? I have some high quality 7 layer 3/4 plywood I can use. I see it's recommend to coat the plywood in resin, is bondo fiberglass resin ok to use or should I be using a specific brand?

some more photos here.

Nice boat and project!

This thread here has all the links needed for rivets and rivet tools and tooling: https://forum.tinboats.net/viewtopic.php?f=3&t=45596&p=457693&hilit=jay+cee#p457693

I'd not use fiberglass resin, as it is terrible on plywood. Use epoxy like that from www.raka.com (download their free epoxy manual) or use a varnish finish like others here use, old timers.

This post here has info on using epoxy and making permanent epoxy 'plugs' that any SS fasteners go through: https://forum.tinboats.net/viewtopic.php?f=3&t=47405&p=480245

For the weld, if that piece can be secured properly by a through-bolt through the new transom, you should be all set.

You need to insulate any SS fastener/bolt used from the tin (or the tin will corrode due to electrolytic/galvanic reaction), by putting a thin nylon washer between the bolt head/nut and tin surface it bears against.

Dale, you are like hitting the jackpot of answers! thanks so much, links and everything.

for your epoxy plugs could you go into a little more detail on how to go about it. how oversized are you making them? lets say for a 1/4 bolt do you use 1/2 inch hole? bigger? just fill them with epoxy when coating the plywood or do you build the holes up in layers? do you use an oversized washer that's bigger than the epoxy plug when bolting everything back together?

Got the rivets and resin ordered and the old transom out. Also got some more water logged foam out, the whole floor was the same way. Boat might be 2 or 300 pounds lighter.

This transom didn't go all the way to the bottom of the boat. Wondering if the new one should? Guessing its to stop it from sitting in water so probably not?

Also should the new transom be glued in place to the back of the boat? Or just bolts only?

I would make it the same size as original, keeps from wicking up water.

Some of the sealants react with aluminium, so the safe thing to do is to just use screws. The motor holds the middle pretty tight, so a couple thru-bolts in the outside corners makes for a good load path for the motor forces.