Re-powering my seacraft

[Bushwacker]

Originally Posted by RUSTYNTABATHA

. . . I thought the motors were rated at the prop in real world HP. 150 =150 at the prop shaft 175=175 at the prop shaft.. if and when i can swing the new motor i will be extatic with 4 + mpg @ 35 mph..

NAEBM rules only require that the actual HP be within +-10% of the advertised HP! BRP appears to be sandbagging by the full 10% on the ratings of their more mildly tuned motors, because they've published HP curves showing that the "150" E-TEC is actually 165 hp at the prop, so it's a very strong "150"! They also build the "175" and "200" hp motors on the same 158 cu. in. block, but I suspect the actual hp of the "175" is about 180-185, while the "200" maybe somewhere around 190-200. The 3.3L"200" HP big block V-6 is reportedly a very strong motor at about 220 hp, but it's also over 100 lbs heavier than the small block V-6.

If you look at HP/cu. in., that'll give you a clue as to how strong the motor really is, especially in the mid range where you want maximum torque for getting on plane. The more conservatively rated motors tend to have more mid-range torque than motors that are tuned for maximum top end HP. One of the most knowledgeable techs on the E-TEC Owners Forum claims that the 105 cu in. V-4 115 is actually has noticeably more mid-range torque than the 130 HP version of the same powerhead! HP and Torque are two different things, and both 2 and 4-stroke motors can be tuned to optimize one at the expense of the other!