I have a 1972 Mercury 50hp Thunderbolt on a 16' Fiberglass Terry Bass Boat. The Mercury cranks and runs like a sewing machine except for one issue. It doesn't seem to top out and will not put the boat on top of the water. As opposed to fooling with it, I purchased a 40hp Yamaha for the boat. What is the 50hp Motor worth? I am going to ebay it and looks like the parts --- which are all good, including controls---seem to be in demand. Any ideas on an asking price?