High Elevation Propeller Options

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Lsnow

Cadet
Joined
Feb 28, 2012
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Does anyone know what prop I should use on a 3.8 OMC at lakes at high elevation. I live at 4500 feet above sea level. I use my boat at various lakes between 4400 and 7600 feet. At 7600 feet there is about a 7 mile an hour max difference from a faster speed at lakes at 4500 feet. I have a 15x17 prop now. Would a 15x15 prop be better at lakes above 6500 feet or so?

Please offer your opinion.
 
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fishrdan

Admiral
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Jan 25, 2008
Messages
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Re: High Elevation Propeller Options

You need to post back with the WOT RPM at both elevations for good prop suggestions. I think the 15P prop is headed in the right direction.
 
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fishrdan

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Jan 25, 2008
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Re: High Elevation Propeller Options

Lsnow said:
At 5400, my wot is 4100 rpm.
Click to expand...

That was quick (You're not part of the Psychic's Network, are you? :D)

I'm not sure what the WOT RPM range is for your 3.8, but 4100 sounds too low. The 15P prop would bring the RPM's up about 400RPM which will be fine. Hopefully, at 7000' you are still 4200RPM, or so.
 
L

Lsnow

Cadet
Joined
Feb 28, 2012
Messages
22
Re: High Elevation Propeller Options

I bought a 15P. Today at a lake at 7400 feet, the boat ran wot 35 mph @ 4400 rpm.
 
jestor68

jestor68

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Jun 12, 2012
Messages
2,308
Re: High Elevation Propeller Options

FYI: HP loss=elevation x 0.03 x rated hp / 1000. It works out to almost 4% per thousand feet of elevation.

Robertson Marine(Salt Lake City) has a web site with a good discussion on setting up boats for high altitude operation.

Since the rpm range for that motor is 4200-4600, it appears that you're good.
 
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