Boat engines are the same as a car engine. I worked at OMC as parts technical help and they bought the engines directly from GM or Ford. A complete engine with carb, alternator (marine) and everything, even intake manifold was 750.00 their cost. THe only difference is the paint color and head gasket which are stainless steel. I also heard, but didn't check it out (because I'm not a techi on that stuff, I just love parts), that the heads were high performance heads and valves due to the high RPM of the boat engines. They run at about 5 to 7500 RPM. I could find out more if you want, and may have saved the cross reference guides for the parts switching from Mercury and OMC to Ford and Chevy. The parts are higher in the boat market though. Gayle