yamaha prop - SS

[crabman333555]

Queston, I have a 14 1/2 X 17 aluminum prop on my yamaha 150 and no issues. I turn about 5200 rpm's. Should be according to manula at 5500 r's..<br />If is swithch to SS prop, do I use same pitch and diameter as I did on aluminum? Thanks

 

[WillyBWright]

Re: yamaha prop - SS

Stainless prop blades are thinner and spin a bit easier thru the water, so a stainless prop can spin a bit easier than an aluminum prop of the same pitch. That'll pick up around 100 RPMs (give or take a bunch). Some stainless props are offered in even pitches. Going down to a 16 would give you another two hundred or so.<br /><br />What boat and specifically which 150?

 

[Boatist]

Re: yamaha prop - SS

Crabman<br />If your Turning 5200 WOT RPMS with the prop you have now and this is with your normal load, not with extra people and gear or just you and no gear then this is a good starting point.<br /><br />Motor are rated for a range like 4800 to 5200. Yamaha 2005 2 stroke 150 is 4500 to 5500. The 2005 4 stroke F150 is 5000 to 6000. <br /><br />If your motor is a 2 stroke with the same rating as above (4500 to 5500) for the 2 stroke then you have the right pitch and size prop. If the stainless prop you are looking at has the same Diameter and same number of blades then you should get the same pitch. A change in pitch of 2 inches will make a change in RPMS of about 400 RPMS. <br /><br />So a 15 inch prop would put you at 5600 RPMS and that would be to high a RPM and also mean faster hole shot and less speed and more fuel used. <br /><br />If you went to a 19 pitch your RPMS would be 4800 rpms, It should be a little faster 2 to 3 MPH use less fuel but have a slower hole shot. I think if it is still in your manufactor reccommended range then it is ok, but many here will tell you should be right near the max rpm range. I personaly feel lower rpms extends the life of your engine. It does in Nascar and it does in autos. I belive it also extends the life of your engine in outboards as long as you are still in the rpm range the manfacture reccommends. Now if you go too high a pitch you could burn a piston and lug the engine.

 

[Boatist]

Re: yamaha prop - SS

Crabman<br />What is it that makes you want to change your prop?<br />Do your want more top speed or do you want a faster hole Shot?<br />Does your current prop have a problem or do you just want a stronger prop?

 

[walleyehed]

Re: yamaha prop - SS

You need to be at or slightly above your max RPM with a light load, or you WILL be lugging it with 2 people and some gear on board.<br />If your concerned about the life of your engine at all, consider a good quality SS in 15", as we can always add a bit of cup to tweak the R's if needed. If it's a high quality prop, you're not going to lose any top-end, but you WILL gain bottom end and engine longevity.