aluminum vs. stainless prop question

[Searun1]

Sorry guys but I have a prop question...<br /><br />I tried using search but did not find what I was looking for.<br /><br />I have a 13.25x17 standard Yamaha aluminum prop on a 90 HP '05 two stroke. The boat is a fairly typical deep v runabout at 16' and fiberglass.<br /><br />I was thinking about an upgrade to a stainless prop and am a little confused. I think I read on this board that the same diameter/pitch prop is different between ss and aluminum.<br /><br />Would I look at a 13x19 or the same size ss? The boat is mostly used for salmon fishing here on Puget Sound with the occasional wakeboard/skiing excursion.<br /><br />Any advice would be greatly appreciated.<br /><br />Searun1

 

[bluewater19]

Re: aluminum vs. stainless prop question

What are your RPM at WOT?<br />If you are within the manufactures recomended rpm range then use the same size in stainless. You might see a little more topend but not enough to go up 2 inches of pitch.

 

[walleyehed]

Re: aluminum vs. stainless prop question

Asuming your RPM is in the top of the max range, I would suggest a Stiletto 13.25X17 if dead-set on a prop-swap.<br />Raising the eng. on the transom can add measurable performance as well.<br />I have been in your shoes with a simular application and went from a 15 pitch to an 18 pitch just by eng. heigth adjustment/mounting location, and actually gained RPM slightly, and best of all, I added 9MPH to my top-end.<br />If you want to play, we can tell ya how....

 

[Searun1]

Re: aluminum vs. stainless prop question

Thanks for the advice. I rarely get to push the speed on this boat anyway due to water conditions. I am getting 5500 at WOT with the aluminum so I will likely go the same size in stainless.<br /><br />I really dont need high performance, just want reliability and better economy. It is a fishing boat for the most part. Thanks again guys.<br /><br />Searun1

 

[walleyehed]

Re: aluminum vs. stainless prop question

Here's an Idea....<br />If you raise the eng., lower drag and are able to spin more pitch at the same RPM, which equates to faster speeds, yet when pulled back you would be attaining the same speed at lower RPM, creating substantial fuel savings....????<br />Hummmmm.......<br />More'in one way ta skin a cat.