Propellers for High Altitude

Optimizing the performance of Boston Whaler boats
Don SSDD
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Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Propellers for High Altitude

Postby Don SSDD » Mon Feb 01, 2021 7:00 am

If a boat engine is losing power at high altitude, should a different propeller for high altitude than used at sea level be considered?
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
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Location: Michigan, Lower Peninsula
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Re: Will Fuel-Injection Improve Engine Performance at High Elevations

Postby jimh » Mon Feb 01, 2021 8:32 am

DON--I believe that changing the propeller to accommodate reduced engine power output at altitude is a common technique used by boaters. To change a propeller takes only a few moments.

Many boaters also change the propeller to accommodate unusual loading situation, particularly on smaller boats where changes in weight aboard can be significant percentage changes in total weight.

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Phil T
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Location: Was Maine. Temporarily Kentucky

Re: Will Fuel-Injection Improve Engine Performance at High Elevations

Postby Phil T » Mon Feb 01, 2021 10:13 am

Don -

If an owner has a carbureted outboard, installing larger jets can help mitigate some of the impact of the air density change. One can also use a lower pitch prop as well but you can only go so far.

In a handlful of cases I know a prop change has helped. In several instances, all high elevation (8,000'+), a repower was required.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

Pogiepika
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Joined: Thu Jan 28, 2021 11:09 am

Re: Will Fuel-Injection Improve Engine Performance at High Elevations

Postby Pogiepika » Mon Feb 01, 2021 7:43 pm

jimh wrote:I believe that changing the propeller to accommodate reduced engine power output at altitude is a common technique used by boaters.


The shop [that is selling me a new engine] said I certainly would need [two] different propellers: one propeller for high altitude, and one propeller for the coast [at sea level]. The shop said they have a lot of experience in getting the correct propellers for high altitude.