Re: Switching from aluminum to stainless steel prop
Badcarma, a boat, unlike a car, has no transmission so the prop must get the boat out of the hole without struggling. It must also allow comfortable cruise rpm and also run wide open with engine rpm at or very close the maximum recommended with what YOU consider an average load. What you consider an average load my be very different than what I or others consider an average load. Each of those loads may require a different prop. Next -- props have many design factors besides just diameter and pitch. Cupping, rake, blade area, blade shape are just few. If you looked long and hard at prop specs you will see that in many cases, within the same prop model, diameter goes up slightly when pitch comes down and vice versa. Besides, prop diameter has little to do with performance -- it is part of the prop design. As Bond-O points out, until you run this boat at wide open throttle with an average load and note speed and engine rpm you have no idea if the prop you have is correct. If you don't know it is currently correct you have no idea whether what you buy to replace it is correct either. If the prop is wrong at WOT it is wrong across the entire rpm band. As for damaging the engine, if 4800 rpm will damage the engine, why do you think Mercruiser set the red line at that RPM? You don't have to run WOT all the time -- that's why boats have throttles. But you do need to run it wide open for testing purposes and to ensure you are not lugging the engine, thus burning more fuel than necessary, and getting poor performance in the process. Do as you are asked for testing and we can help. Without test data you get "speculation".
