I wouldn't chance it - and I wouldn't chance Secast bonding to wood either. If you're going to leave wood in the transom (which I don't recommend), soak it well with resin and make your pour when the resin is still green. In fact, coat it once and let it set then coat it again. This should go a long way toward proper adhesion. Arjay and Nicacore pour like latex paint. From what I've seen, seacast pours like chunky vomit. I used a rubber mallet on my transom to release any air pockets, but it wasn't necessary. That stuff filled every void with ease. Make sure EVERYTHING - even the smallest hole is sealed. It will run everywhere.

I did not read this entire thread but if this is the boat I would just remove the inner shell. It looks like you have removed everthing that needs to be removed and all you need is a large tree limb, a pully, rope, and a truck. I took out my inner linner to replace my transom and after I got all the stuff off of the boat it only took about 1 hour to get the linner out and most of that time was rigging the pully and lines. You can then inspect the runners and the florring of the boat.

HI again.
I know you all may be tired of me changing my mind on this transom =) but I have finally decided I am going to do a full traditional transom replacement using coosa board. I am going to do it from the inside. A friend of my dad's that now manufactures boats with what used to be the manatee boat molds had a chance to come and look at it for me and this is what he recommended. He said there wouldn't have been any way for me to remove all the wood from the top because it was only rotted in a small place and the other wood had been bonded well. Also because I wanted to make it a full 25 inch transom the pour method wasn't the best method in this situation. I hope I will have an opportunity to begin this weekend. I'll take some good pictures as soon as I begin =).
I was wondering. When cutting fiberglass with a cutoff wheel of grinding it with a grinding wheel do you use metal cutting wheels or masonry wheels. I had been using metal but I though maybe someone may have tried both. thanks guys.

So are you going to cut the rear of the inner linner or are you taking the two section apart.

Cut the rear of the inner liner. This had been done before by a repair company to replace the transom the first time and I need to fix their finish work anyways.

I still think now is a very good time to take the boat apart and check the stringers at the same time. You have everything done to just take the boat apart and its easy from here.