1970s princecraft transom repair

Hi there, yesterday evening I picked up this 70s princecraft 11 footer. I wasn't expecting to buy a boat yesterday, but in my area they rarely pop up in my tight budget so I kinda jumped on it.

Amongst other things, I think the transom needs attention. The wood isn't soft, but it's very dry. The corner brackets are also loosely pop-riveted on, one handle is broken and the other is cracked so those will need attention.
It's rated for 7.5 HP. I already have a 1975 Evinrude 15 hp, is there any way I can build up the transom to better take the 15 hp motor? Or would I be better trading down to a 9.9? I don't have any way to weld aluminum short of those aluminum brazing sticks and a torch, but I do have other metalworking tools and woodworking tools as well.

Cheers, David

Wood - Nothing to lose, for this season, by coating it with any exterior paint or finish, like even a good deck stain.

Corner Braces - McMaster-Carr sells some awesome 1/4" high strength/high shear 'pop' rivets that hold incredibly well, but are only found in quantities of (25). I could sell you 6 or so, but you really need the large 'A'-frame rivet tool to set them. See if you can through-bolt secure them with a SS bolt.

HP - With no hard chines or fore/aft lifting strakes (that also provide rigidity) on on that hull, it is a lightweight, low HP hull only and I fear it would be a FAST, but deadly tippy-canoe! I tried a 15hp on my tin hull that looks better than that one and it was a no-go in regards to safety. Most interestingly, I only gained 4mph @ WOT over an 8hp and the HP difference wasn't fully realized until 2 people were in the boat, where the 15hp would keep it up on plane nicely. But I switched it out to my 8hp.

I'll include a photo of the bottom side for reference, but if you and others here don't think it's rigid enough, I'll tune up my 15hp and try to trade down to something like an 8-9.9

I'm not looking for speed, I already have that 15hp and was just wanting to make do with what I had.

I am looking to replace the corner brackets, as the ones on it had the handles as part of the corner, and ones gone and the other is cracked badly. Are there any suppliers for new corner brackets?

You can always use it and just not run it WOT; I'd just hate to see it get squirrely on you, never mind cause an insurance issue God forbid there was ever an accident! And believe me, checking out the boat and its rating is the 1st thing they do.

I'd advise you to add an extra 4-6" tall piece of wood across the full transom (inside) if you do. Again, I/we don't know what load you're carrying.

Fair enough. My wife and I are just kinda hobby fishers, her more so than me. I just enjoy getting out on the water for a change of scenery. Most load would be us and a couple rods, small tackle box and maybe a small cooler.

I've heard with the older evinrudes, the 9.9 and the 15 were essentially the same apart from carburetor, I'll have to do some research on that. But you're right, that doesn't change the legality of it all, cause the model code would still show as a 15hp. I might use it a couple times just to make sure the boat does what it should, and the motor as well, then look to trade down to an 8 hp or something

Well I was talking with a co-worker, who knew a guy that knew a guy, and I wound up trading my old 15hp for an older but nicer Johnson 10hp. Still maybe not ideal, but at least a step in the right direction.

I'm also talking with a welding shop to make me up some new transom corner caps. I might also double up on the plywood for now