20SC w/ 115 #'s and opinions needed

[Bushwacker]

Originally Posted by McGillicuddy

. . . A stainless will typically be harder to turn so you would have to go to a prop of less pitch. Rule of thumb for same prop shape, drop 1"-2" of pitch for stainless. . .

Gillie,

My experience, at least with Michigan props, is that they're able to make the blades thinner on the SS props, so they're actually EASIER to turn than the same size aluminum. When I started trying 4 blade props, the local shop recommended a 14" dia x 20" pitch aluminum Vortex prop. The equivalent SS prop was the 4B Apollo, but they made it slightly bigger at 14.125" diameter x 20" pitch, I guess to compensate for the thinner blades. I could turn both props to the same rpm with same load, but the SS prop was about 3 mph faster!

When I was running the old 115 on my boat, the 13 3/4 x 15p OMC SST prop turned about the same rpm as the same size aluminum prop, but the SST had a lot more cup in the trailing edge. I was able to raise the motor 1 hole and also picked up about 3 mph with the SST. It was an excellent prop and the 15x15 4B SS PowerTech prop I'm now running supposedly has the same blade profile as the old SST. The 15x15 4B prop seems to be very efficient and runs about 4-5% slip at optimum cruise! Denny