I have a 1981 20hp Mercury. I had it on a 16 in transom boat. I had to raise the motor 2 inches to get the cavitation plate almost even with the bottom of the boat, it was still a little low. I now have a 20 in transom boat. When I put the motor down on the transom it is 2 inches short. I have measured the motor from the mounting bracket to the cavitation plate and it is 18 inches. Has anyone ever heard of this? Is it an oddball? or was this a normal length for this motor?