Seacast, Arjay 6011, Nida, etc.
The bottom of my transom is shot in this boat, way too hard to split the deck to get access from the top and full inside access so I'm considering filling it up with seacast. I already went in through the I/O hole and used an auger bit to remove the wood in the center section of the transom, but the outer sections are angled enough that I can't get a bit in there. I used a pressure washer to blast out the trim tab holes and they are all connected (entire bottom of all transom panels are rotted out and gone). Original plywood was 3/4". The crack at to bottom of the I/O hole is of moderate concern, however I think once there is something solid behind it, it should be okay after getting vee'd out and filled with epoxy/csm.
PSA, a 15hp pressure washer with the single stream tip can delaminate fiberglass if you hit an existing hole.
Option 1: Pour it as it is, the outer sections should be fine left alone, assume the pourable will find it's way to the entire bottom of the transom. If it doesn't then inject it later.
Option 2: take an upside down "T" section out of the inner transom.
I was using this boat last year with no signs of issues, but when I was getting ready to float it this spring I noticed the crack at the bottom of the I/O.
Save the boat ownership jokes, I got it for free and I've used the hell out of this thing over the past 6 years I've owned it and it has always been a reliable fish catcher, if not the prettiest.
Looking for anyone with actual experience, I can find boyscouts on the marine forums.