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Prop specs
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Author:  Hobie [ Sun Sep 05, 2010 1:25 pm ]
Post subject:  Prop specs
I have a 15x16 prop on the following setup:
262 CID
4.3 liter
V6 Chevy
Cobra Outdrive

Is this prop appropriate for this engine?

Is the prop designed for hole-shot performance, or high end speed?
Author:  Cap'n Morgan [ Tue Sep 07, 2010 6:17 am ]
Post subject:  Re: Prop specs
What is your WOT RPM's ??
What boat is this on ?
What is you drive ratio?
What altitude do you boat at ?

Props are designed for a specific engine/outdrive application. The one that gives you the
recomennded RPM range at WOT is what was designed for you power train. From there, you can
chose to modify what prop you put on, based on your needs.

That engine/drive probably came stock with a 15 x 17 3 blade aluminum. prop, for area's that are
closer to sea level.
Author:  Hobie [ Tue Sep 07, 2010 9:53 am ]
Post subject:  Re: Prop specs
Cap'n Morgan,

WOT RPMs: I had it up to about 4500 but didn't keep it there long enough to see if it had any more juice.

Boat: 1988 18' Horizon

Drive ratio: I have no idea [newbie]. Is this something that I can check myself? The outdrive is an OMC Cobra.

Altitude: 5280' Denver.
Author:  powellcrazy [ Fri Sep 10, 2010 8:23 pm ]
Post subject:  Re: Prop specs
gear ratio is stamped on a plate on side of drive.

prop 15 X 16 15 is the diameter and 16 is the pitch. pitch is how far the blade advances in one full revolution. 16 pitch is low, good for holeshot, poor top end speed. But, most important that your engine is in the proper RPM range at WOT. You can find the proper engine WOT RPM in your owners manual. (if I were to guess, 4500 - 4800 rpm)

21 or 23 pitch would give poor hole shot, but may give more top end. there are many factors, you can not just go throw on a 23 pitch and end up with a 60 MPH boat. If you are reaching the top end of the MFG recommended max RPM at WOT, you could try to go up 1 or 2 pitches, but know that this will affect your hole shot.

Since your boating at high elevation, you will need a prop with approx pitch. For every 1000 ft in elevation gain your engine losses approx 5% power.

My boat is an absolute DOG at 7000', but when I goto powell (3700') it performs ok. But I can reach the recommended Max RPM at both elevations, barely, I am not going to reprop for the occasional very high elevation trip.
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