Dive on the prop, it could be barnacle growth. But if the prop is clean then I would play with the pitch. I am not going out on a limb and tell you that this could not be damaging. What I do know is if it is not taken care of it will get worse. BTW, when I am motoring I am at half throttle or about 2200 rpm. That seems to be the sweet spot for my boat where the engine is the smoothest and I get the best fuel consumption 1/4 gal an hour. The difference in speed is 5.4 knots compared to 6.2 knots at 3/4 throttle and using 1/2 gal of fuel an hour.
Last edited by bubb2; 05-28-2011 at 08:12 PM.