Choosing A Prop For Higher Elevations
When wakeboarding or wakesurfing at high elevations there is a noticeable decrease in the power output at wide open throttle. Air contains less oxygen at higher altitudes resulting in a much longer amount of time it will take the boat to get up on plane. Additional ballast, beyond what comes from the factory, will exponentially add to this problem and may limit the boat from planing out at all. An upgraded propeller designed to be more efficient at higher altitudes is the answer. High altitude props have a lower pitch and an increased diameter which will facilitate regaining low end hole shot and higher RPM's. The intention is to help decrease the strain on the motor by lessening the time the driver must be at wide open throttle before the boat will come up on plane. A common result of using a performance based propeller is a top end speed decrease of between 5 and 10 MPH.Example
We wakeboard behind a 2011 Malibu VLX (Monsoon 340HP Motor) with the Acme 1939 prop (14” x 15.5”) in Southern California (Elevation 300 ft.). We run two 400lb. Sacs in the rear compartments giving us 2000 lbs of total ballast. Our top speed is right about 44 MPH with a comfortable cruising speed of 34 MPH.
When boating at Lake Powell (Elevation 3500 ft.) we upgrade to a prop that will be better suited for the higher altitude. We could see around a 10% HP loss. That is huge since we wakeboard with about 2000 lbs of ballast in the boat. By upgrading the prop to the Acme 2079 prop (14.5” x 12”) there will be a noticeable increase in power at the low end. Our top speed is decreased to 38 MPH, and our comfortable cruising speed is decreased to 28 MPH.
Use the follwoing equation to determine the typical output of your motor when running at higher elevation:
Horsepower Loss = (Elevation x 0.03 x Stock Horsepower @ Sea Level) / 1000