RE: 4 stroke boat and nos
I have to agree with Amax on that one. A four stroke aircraft engine will give more raw grunt at lower rpms that allow a plane to run a larger, higher pitched prop, providing more thrust than the two stroke of the same size spinning at the same RPM. When you consider that the average aircraft engine tops out at around 17K to keep the prop in a usable RPM range, this is totally different than a marine engine that spins up to between 25 and 30K for engines of .45 or larger and up to 35K for smaller. To take this one step further, an airplane engine of .20 to .25 will spin a prop size of around 8X4 to 9X6. A comparable marine engine would spin a prop of around 40mm in diameter with a pitch of around 50mm. You also have to remember that a four stroke normally burns fuel of under 10% nitro while the average boater runs a minimum of 25% and racers run up to 70%