When I bought my boat this spring the previous owner was quite proud of the brand new transom he had installed.  Solid oak he pointed out. It's an aluminum boat with a wood transom.  The original transom had a dip in the middle where the motor is mounted.  The new transom is flush straight across, which I prefer.

 

Anyway one of the first times I had the boat out this spring the transom developed a small horizontal crack that followed the grain of the wood.  I installed a mending plate right where the motor attaches but despite that, the crack kept getting bigger and wider to the point where It needs replacing.

 

Obviously oak isn't a good material. What does everyone suggest?  Is there a synthetic material available?

 

Here are a few pics. It doesn't look real bad, but when the outboard is on and running the crack gets a lot wider

 

Marine grade plywood

Marine grade plywood

X2 

Marine grade plywood would probably be the cheapest.  Another option might be some of that plastic, composite wood, like high dollar decks are made with.  I have some plastic ultimate bunk boards on my boat trailer and I've been happy with them.  

Marine grade plywood would probably be the cheapest.  Another option might be some of that plastic, composite wood, like high dollar decks are made with.  I have some plastic ultimate bunk boards on my boat trailer and I've been happy with them.  

Marine grade plywood ain't cheap. I think the plywood is a better option than anything solid because it will allow some flex. The solid oak he had cracked because there was no flex.

X2 

 

Marine grade plywood

 

X3

X4 on the marine plywood. Also there is a composite call starboard (I think) Its like a cutting board material. I've used that over plywood on transoms as a pad for the motor.