Re: need Help with Transom
Sad to say, but WOG is right. If your transom is that rotted, then likely the deck will also have issues. Sadly, if the deck has problems, then the stringers and bulkheads will also need to be addressed. There is no sense in replacing a transom only to attach it to rotted stringers.
From the images that I've seen via a Google search, that model has a fairly large splash well in the back. Sometimes you can do a rebuild without popping the cap bit the line between the cap and the hull isn't high like on a lot of boats. Here's a side shot that I found out there.
It looks to me like pulling the cap wouldn't be that hard to do, but I know nothing about Glastron boats so anything that I say is pure speculation.
If you get into the floor and find that the stringers are wet or rotted out, then you'll have to make the decision to scrap it or put the time and money that is involved for a restoration. Restorations aren't cheap and they require a lot of man hours. Yesterday was my 31st day in a row working on mine and I'm about halfway done. I'm also in for around $2K in materials (I opted to go the epoxy route which is more expensive).
BUT there is no doubt that I will have a boat that is better built than the one that came from the factory. You can too. Just don't be discouraged about taking it on as a project since it was your Grandpas boat.