Re: first timer transom replacement need help
The simple answer is that you can use pretty much whatever you want for the transom - but doing it right is actually a lot easier.
Dimensional lumber isn't the correct size and so the correct way is to build up the exact thickness required using sandwiches of ply and fiberglass. It's strong and will be the correct size. Pourable materials such as SeaCast are strong and rot free but more expensive - so if you plan on handing the boat down to your kids in a few years then it makes sense - if like most of us, you keep the boat for a few years and then upgrade then it's probably not worth the extra expense.
There must be 50 threads showing how to replace the transom so plenty to read