propellers, from aluminum to SS

[hoavannguyen]

I am considering changing my propeller on 100HP Yamaha 4-stroke from aluminum to Stainless Steel. I have no knowledge regarding this change except from my reading. I like to hear any comment on type and performance of different brand of Stainless Steel blade. I am running 13 1/2 x 15 Aluminum blade at this time with WOT of 5500 RPM ( Max of 6000). Thanks.<br />Hoa

 

[wtrojan]

Re: propellers, from aluminum to SS

The performance will depend on the hull and setup you are running. The SS prop of similar dimensions would give you usually about 100rpm more on average, comparing to aluminum. If you are aiming to reach the max rpm at WOT, you’d probably have to drop the pitch by two inches (to pitch 13) which would give about 400rpm more, resulting in about 6000rpm total. All this assuming you are trimming the engine ok and more importantly, that the height of the engine on the transom is correct – the anti-cavitation plate (the biggest plate on lower unit) should be in the range of one inch below to one inch above the keel, the latter being the good point to start the transom height tuning. Have a look at general discussion board, there is a big thread about this going on right now. And about the SS prop selection, click the “props” link above, this could help you find one.

 

[Spidybot]

Re: propellers, from aluminum to SS

Agree with spearo.<br /><br />Nomally the hunt for a new prop starts with identifying some kind of problem. Some kind of 'not really happy with it' - or worse.<br /><br />Once you know what you're looking for, several ways of getting there may be available.<br /><br />Any prop is reprensenting a mix of compromises. It is like a gear in a gearbox or on a bike: It's either good for pull (accelleration) or for top speed. Unless you go for a switching pitch prop (like having a two automatic gears), you're stuck with this fact.<br /><br />The science is to get the compromise that suits your needs and this involves mounting height (so called x-dimension), pitch, prop design, prop material, number of blades, trim and boat optimising (like throwing un-needed weight out or moving weight in the hull).<br /><br />Feel free to get the free booklet on props from my homepage.