High altitude boat moving to sea level.

Schuster

Does anyone out there know what I should expect when moving a boat that lives at high altitude (5,000ft) and move it for operation at sea level. Will it run stronger or weaker?

garyf · Posted: Sat May 01, 2021 2:50 pm Post subject:

I'll be interested to see the other replies, but I think it depends on the current prop. If the previous owner took time and effort to prop it for high altitude, there might be some room for improvement at lower altitude. If the current prop was intended for sea level, then it'll probably run a bit stronger.

Without any other influence like that, it should run a bit stronger in general.

Hunkydory · Posted: Sat May 01, 2021 3:50 pm Post subject:

Our primary boating is done at sea level & Yellowstone lake at 7733 feet. In between it’s all 6 to 7 thousand feet except for 3563 foot, present lake Powell. We’ve been going up & down these elevations for the now 19 seasons in our CD 22. You lose about 3 % of hp for every 1000 feet of elevation gained, so on Lake Yellowstone our combined 60 hp Honda’s of 120 hp are putting out only a max of 95 hp. To carry heavy loads on Yellowstone Lake, I use a 13 pitch three blade prop. Lake Powell to sea level 15 pitch. If ones prop is pitched on the high side, but workable at sea level, many will have to drop pitch for Lake Powell & definitely for Yellowstone Lake. The opposite for going high elevation to low. You will definitely have more power & probably will need to go to a higher pitch prop to keep from over rpming the motor by going from 5000 feet to sea level.

Jay

thataway · Posted: Sat May 01, 2021 9:42 pm Post subject:

You will want to get max speed at WOT. What is the speed of the boat and the RPM at wide open throttle (engine and boat will help).

Generally increase pitch 2"--but it is possible that you may be able to increase pitch 3 or 4 inches...But we need to know the numbers.

C-Green · Posted: Sat May 01, 2021 10:59 pm Post subject:

Not a worry for most but if your engine is carbureted, jets may need to be replaced.

Jay

Schuster · Posted: Sun May 02, 2021 11:16 am Post subject:

Good info, thank you. I don't have numbers yet, but will be looking into this more when I do. Thanks everyone, you have been very helpful.