In the middle of a cat rebuild and have no idea what I'm doing, but I'm figuring it out. There are some places that have obvious rot but others that "seem" good but I really don't know. The main area right now in question is the area between the spray rail and the top of the tunnel. See pic. Someone cut it with a saw and never repaired it. The balsa? below it is gone and I really have no way to tell how far the wetness goes. So far I have cut some 2x2 holes to see but I'm wondering if there is an easier/smarter way. A test cut on the other sponson showed completely dry wood.

Also, what is the best way to check the transom? There is a 1/2" aluminum plate on the inside and outside of the transom that was added to help support the weight of the big V8 o/b's. Any help is greatly appreciated.

George

i use a 1.25 inch diamond hole saw used for tile work with the center drill taken out to do test holes. Drilling several holes throughout the boat is the best way to find the bad spots.

Thanks Dave, if it's limited to the rear quarter of the boat, should I only recore that area? That sponson? Should I use balsa again or it there something else recommended.

yea you can spot core in. I prefer to make it as symmetrical as possible though.