Do I have a transom problem?

I have a 1988 procraft fish and ski 1780 with a 1988 150 hp merc black max and a jack plate. When I place a straight edge across the top of the transom, there is a 5/8" deflection noted. I thought this was a major problem but after further investigation, I'm not sure. I checked the wood at the top and around the top engine mounting bolts and there's no indication of any wet or soft wood in the transom. Also, if you pick up or push down on the motor, there is only minimal flex noted (approximately 1/32" measured). I also tried to straighten the transom deflection with a 1 1/2" by 6" piece of solid oak that spanned from one end of the transom to the other with only partial success. I was able to take out about 3/8" of the deflection but I put a 1/4" deflection in the oak board when it was clamped tight to the transom. Is this something I can live with and should any type of reinforcement be added? Anyone have any thoughts?

Re: Do I have a transom problem?

If you apply constant, sufficient pressure to wood, it will eventually bend. The transom was probably straight when the boat was built.

Many older transoms take a set from the weight of the engine hanging on them. Look for cracks in the fiberglass in the splashwell. When the transom moves, usually the splashwell cracks in some places near the transom. The oak will definitely flex: Remember it is 1 1/2 inches thick and the transom is 2 inches thick so the oak will flex more than the transom.

Preventive and corrective measures I apply to all my boats are to bolt a piece of 2 X 3 inch X 3/16 or 1/4 thick aluminum angle onto the inside of the transom for its full length with the 2 inch side across the transom top. I had to buy 3 x 3 and cut off 1 inch from one side. I use a 3/8 bolt through the transom in the center, and two sets of 5/16 bolts on either side of center, for a total of 5 bolts spread evenly along the length. This will draw up the transom with minimal deflection to the aluminum angle. Use exra thick fender washers if you can get them and self locking nuts. Of course, all Stainless. Go to your local welding shop to buy the aluminum; don't get cheap grade.

I was also able to get my hands on some 2 X 6 inch extruded aluminum C channel --free. The sides are 1/4 inch and the web is 3/16 thick. A hunk of this with one side cut off is going on my next transom.

Re: Do I have a transom problem?

Thanks for your input. You confirmed my own feelings about the transom and that helps. I like your suggestion about the aluminum reinforcement across the top.