Prop for high altitude

[Kevin Ford]

I'll be fishing this year in some high altitude(6000ft), running a vmax 225 hpdi. Anyone have any experience in loss of performance at that altitude with that motor? Its got a 3 blade 25 pitch prop on it now and I'm considering buying a 4 blade 23 if available.

Any thoughts?

[boscoe99]

My thoughts are that you are not going down in pitch enough. Particularly given that you are going from a three blade to a four blade propeller.

[Kevin Ford]

What would you recommend?

[boscoe99]

What is your WOT RPM now with the boat loaded at sea level?

[Kevin Ford]

5600-5800 at sea level

[rodbolt17]

try contacting a Yamaha dealer in the high altitude area.

you will find,unlike carbed engines, that HPDI wont suffer as bad due to its baro sensor.

[boscoe99]

Even with an HPDI and its fuel injection system adjusting for ambient air pressure wherever it is used, going from sea level to about 6000 feet is going to result is a loss of about 40 HP. Pretty significant. Throw is some higher than normal temperatures and humidity, and it will only be worse.

How long will you be using the motor at high altitude? Reason why I ask is because a four bladed stainless steel propeller, if this is what you have in mind, is going to cost some bucks.

Why four blades and why stainless, if this is your intent?

If it were me, and if the usage is going to be more or less temporary, then I would consider an aluminum three blade propeller. The choice is up to you of course.

If I were to gaze into a crystal ball I might suggest a three blade with a 21 inch pitch. Why? because I prefer to have a motor be under propped rather than over propped. Remember, the HPDI does not have a knock sensor and if over propped the motor is at risk of detonation. The HPDI does not have a good track record when it comes to detonation of cylinders.

If you are under propped somewhat then no harm no foul. Simply don't exceed the redline of the motor if it is possible to do so. Just pay attention to the tachometer. Now if you are over propped you won't necessarily know it and the motor could (repeat could not will) be harmed.

Your choice of course. But, as Mr. Bolt suggests, also contact a dealer where you will be boating and ask him what he recommends for use at 6000 feet. Then, go down two inches of pitch from whatever he tells you. Dealers and boat builders are notorious for over propping motors.

Good luck and good fishing.