Quote Originally Posted by brettw View Post
Thanks
I have a 3 blade 13.25x19 SS prop and can trade it in to the dealer. It drops the motor down to 5000 rpm, which I fear could eventually damage the motor.
Trade it for a 17 pitch?


Sent from my iPhone using Tapatalk
Generally to stay at the same rpms, you would increase pitch going from 4 blade to 3 blade, so the 17 pitch would be the logical option. Would probably get you around 5500-5800ish rpms and a few mph. If 6000 is your max rpms, you'll want at least 5500 with a light load. That way when you're loaded with people and gear you'll still be in rpm range.
BUT, stainless and aluminum can be 2 different animals. Some stainless can be very aggressive with lots of cupping and rake making the prop have more 'traction'. Most SS props have cupping except for the cheaper general purpose SS which are more for durability than performance.

For example assuming you had a plain jane 3 blade 17 pitch aluminum getting 6000 rpms, an aggressive cupped stainless 17 pitch could be 5500 rpms because it's more 'efficient'. Generally speaking you would drop pitch an inch or two when swapping from AL to SS to stay at same rpms. Lots and lots of variables.