Got myself a project boat - an '84 Wellcraft 248 Sportsman. Now, I grant you that it is not a wooden boat, per se, but I will need to do some woodworking to get the boat I ultimately want.
As originally configured, it came with an I/O powered by a 350 V8. Well the idiot that had it previously didn't bother to remove all the drain plugs on the block - not a good idea in New England. So I trashed both the block and the outdrive as I prefer O/Bs anyway. So I now have a Johnson 200 V6, as well as a smaller Johnson 25hp as a kicker/trolling motor/emergency backup. The 200 will be mounted on a Gil bracket.
Anyway, my question relates to repairing the hole in the transom left after removing the outdrive. I plan to bolt a piece of 1/4" thick stainless steel plate I just happen to have laying around to the inside of the transom, and then to fill the hole with layers of 3/4" ply/fiberglass cloth and epoxy resin. I even plan to do a three stage stepped plug - the first step (against the stainless plate) will be about 18" square. The next step will be about 20" square - fitting into a ledge I'll rout flush to the first layer. The third layer will be about 22" square fitting into a second ledge.
To take the stress of the outboard pushing on the reconfigured transom, I know that I need to add a pair of knees extending up from the floor stringers along the inside of the transom. My question is: what is the best way to make the connection between the stringer and the knee? The existing stringers are 3x6's, so the knees will be white oak 3x4's or 3x5's. I plan to use a fairly large stainless steel lag screw angled through the knee to pull it tight to the top of the stringer, but I can see that some form of gusset along both sides of the joint would add substantially to the strength. Marine plywood, or more stainless steel plate, would be the obvious choices, but I was wondering if anyone had other suggestions - either for material(s) used or even an entirely different way of doing this.