Create a New Forum Admin Login Member Login Contribute to Voyager Search VoyForums Help Desk VoyForums Exchange VoyForums Directory/Categories VoyForums Homepage VoyForums News FAQ - Frequently Asked Questions

[ Show ]

Support VoyForums

[ Shrink ]

VoyForums Announcement: Programming and providing support for this service has been a labor of love since 1997. We are one of the few services online who values our users' privacy, and have never sold your information. We have even fought hard to defend your privacy in legal cases; however, we've done it with almost no financial support -- paying out of pocket to continue providing the service. Due to the issues imposed on us by advertisers, we also stopped hosting most ads on the forums many years ago. We hope you appreciate our efforts.

Show your support by donating any amount. (Note: We are still technically a for-profit company, so your contribution is not tax-deductible.) PayPal Acct: Feedback:

Donate to VoyForums (PayPal):

[ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1 ]

Subject: Prop question Author: JD [ Next Thread | Previous Thread | Next Message | Previous Message ] Date Posted: 7:44pm Q.Stainless Steel Prop vs. Aluminum" I have a Seaswirl 2300 powered by a 1999 Evinrude 200 hp FICHT engine, and I still have the original factory equipped aluminum prop on it. I’ve been told that if I upgrade to a 4-blade stainless steel prop that my performance and fuel economy will improve. Any thought on this? How do I size a 4 blade stainless prop to this engine? Thanks in advance, Hfactor A.A few things.... Four blades are for high speed, not effeciancy. More blades means more drag except in some instances at high speed where drag is reduced due to fluid dynamics. Essentually some four blades use the wake of each blade to reduce drag for the next blade in theory reducing drag for the prop and increasing thrust. It's complicated, doesn't always work, works only a a specific RPM and is way too hard for me to explain. I.E. Unless you're an expert stick to three) Stainless props effectively increase the pitch because they don't flex as much. Aluminum props do flex which is easier on the drive train. They do need a higher pitch to do the same job as stainless prop. The big issues with Props are diameter and pitch vrs load and speed. How off how much does your boat weigh, and what's on it now? 2500 lbs maybe a 14x19 3500 lbs maybe a 14.5x17 6500 lbs maybe a 15.5x15 The first number is how big around it is the second is the travel per turn(in theory). A fourteen nineteen is fourteen inches in diameter and travels 19 inches foreward minus slip. All props slip, but stainless slip less so a stainless 14x19 performs like a aluminum 14x21. What's you boat doing now? Revs up to high: (prop outruns it's own pitch) You need a higher pitch. You can get this in the same size by going stainless, or by buying a increased pitch Aluminum. Bogs down, won't come up to RPM: (pitch is too great to turn against the load) You need less pitch. Eradic, spins good especially downswell but won't hold speed drops off plane or has bad economy: (prop is slipping because it's too small) You need a larger diameter prop. Most motors come under propped diameter wise and over pitched for use offshore. We load up our boats and encounter rough seas. Think of the prop like a tire. You need a lot of traction to push a big load up hills. Traction comes from diameter not pitch. Pitch reduces drag at high speed but increases the load at lower speeds. I'd say 90% of the time I've seen increased performance especially economy by not increasing the pitch, but decreasing pitch and increasing diameter. If your going over 30 knots a high pitch stainless may be the answer but if your cruising at 20 knots it will actually make your economy worse. Just because it will take more effort to turn it. Good luck. Tight lines Jim [ Next Thread | Previous Thread | Next Message | Previous Message ]