CONTINUOUSWAVE

If a boat engine is losing power at high altitude, should a different propeller for high altitude than used at sea level be considered?

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.

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.

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.