Re: 40 Merc upgrade to 50?
That motor cannot be upgraded to 50 HP. It has ALWAYS been a 50 HP rated at the power head or 40 HP at the prop in later years. (A real healthy 40 too..)It is a very old cross scavenged engine with very unique induction sytsem from years ago..It was the last of the "old style" engines. As JB said, if you want more ponnies in this case, another 3 cylinder 2 cycle 59 cu. inch is due. Same identicle power head is used on Merc 40, 50, 60 HP. Each has bigger carbs than the preceeding HP model, 40 oil pump is different from 50 and 60, 60 has some additional porting work done to the head and 60 has different motor leg. These are large cu inch displacement engines for this range with PLENTY of torq. They are also very light for thier HP ratings. The 60 cowling is phyisicly smaller than the 40 and 50.
