Here is my situation: I was driving along and seen the tell tale sign of a bass boat for sale (sitting near the road) so I stopped and talked to the owner about the boat. It is a 1988 18 foot procraft with a Mercury 150 Black Max on it. The upper end on it is shot (a loose nut got in the cylinder and ate the piston then shot it out the side of the case), so I was a little bummed, then he said he had another Mercury 150 x4 that the cylinders could be bored out and should be fine. My question is if I get them bored do I need new pistons or would they just put a bigger ring on the existing pistons? It is a sweet deal, the boat needs new carpet but that is it. It will come with 3 props (one is a $500 5 bladed prop), 2 Mercury 150 Black Max's, cover and all the electronics. It is a 1988 procraft 18 footer. What do you guys think about the motor and how much cash would it cost to get repaired? Thanks for any input.