Ski/Parasail Prop for 21' Seebold

IslanderVT

Seaman Apprentice
Joined
Mar 13, 2013
Messages
48
Tried searching but could not find the answer to a question about the maximum diameter prop for an Alpha 1 drive.

Have a 21' Seebold sport boat with a Mercruiser 260 (Chevy 350). Hull is a pad-keel, step-transom design similar to many bass boats. Currently use a Stiletto 14.25x23 prop for general use. Top RPM's are ~4600 and its a good all-around prop that provides great performance and fuel economy. Top speed is ~60MPH, but hole shot is a little slow.

Looking at options for a lower pitch ski prop, probably aluminum. Thinking 4 blade with large diameter. Have plenty of power...so trying to use that power to create pulling torque. Could use lower planing speed also...we have a parasail we sometimes pull and we find that we need to stay right at minimum planing speed, which is awkward to control.

What is the largest diameter prop that will fit on an Alpha 1 that already has the narrow trim tab needed for a S/S prop?

Any recommendations for my application? I'm thinking a 19 pitch 4-blade in the largest diameter I can fit, and probably a standard aluminum prop in the under $150 range.

Thanks!
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Ski/Parasail Prop for 21' Seebold

I believe a 16" is the largest prop that will fit.I think the extra large diameter is unnecessary.
May be hard to find as typically a 4 blade will have a reduced diameter.
A 21" 4 blade like a Solas Amita should work well.Will improve hole shot and stay on the edge of planing speed with less fuss.
also may handle better around the dock.At 21" you'll probably have to watch the rpm.
 

Bondo

Moderator
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Apr 17, 2002
Messages
70,468
Re: Ski/Parasail Prop for 21' Seebold

I believe a 16" is the largest prop that will fit.I think the extra large diameter is unnecessary.
May be hard to find as typically a 4 blade will have a reduced diameter.
A 21" 4 blade like a Solas Amita should work well.Will improve hole shot and stay on the edge of planing speed with less fuss.
also may handle better around the dock.At 21" you'll probably have to watch the rpm.

Ayuh,... It's exactly 8" from center of the prop shaft to the bottom of the cav-plate, so a 16" prop would be really close,...

The Biggest I've seen is a 15.5x 15",... but the pitch would be Way too low,...

I'm with you though, pick the right design, in the right pitch, 'n the diameter will work itself out,...
 

IslanderVT

Seaman Apprentice
Joined
Mar 13, 2013
Messages
48
Re: Ski/Parasail Prop for 21' Seebold

Thanks for the info....I came to the same conclusion about larger diameter when I started shopping around for options...most 4 blades are a tad smaller dia than the equivalent 3 blade. That makes the diameter question irrelevant...only a few options.

On the 21" pitch, wasn't sure how much difference that would make. I'd be going from S/S to Alum, so figured a 3-4" lower pitch would be better. I'll try borrowing a 21" and see how it runs. Not as worried about exceeding RPM's....this will mostly be a water sports prop so easy on the throttle compared to the speed prop that is sized for the engine.
 
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