[noblealloy]

Hi all - I'm looking into buying a z275st at sea level and bringing it to Colorado at 6,000 ft elevation. First, I'm wondering if anyone has trouble pulling a skier with this boat with a 6.2 merc bravo III duo prop. Second, should I plan on a certain pitch of the prop or adjustments to the engine to bring it up here? Not sure what pitch the prop is yet. Thanks for any input!

[ColoradoDiablo]

The only problem you'll have , is not being able to pass by a fueling dock.
There are a few guys that have a setup like the 275 that I am sure will chime in to help you out with adjustments and Duo Prop choices.


Welcome to MOC!

[mikeyt]

There is no question that altitude saps power. If you have a carbed boat the carb will likely need to be re-jetted to a smaller size & i believe i read that for every 2000 ft increase in altitude from sea level, you can reduce the jets by one size. You may also have to lean the mixture out a bit also to help it idle better as well as advancing the timing about 1/2 degree for every 1000 ft altitude increase. And re-propping is likely a necessity.

Just as one more tidbit of info, i also read that for every 1000 ft in elevation, your engine loses 3% of its power in stock form so at say 6000 ft, you are losing approx 18% of your power without making any adjustments which means a 300 hp engine just dropped to 246 hp.

[noblealloy]

Ouch!

[luke7575]

I own the Z302 and i ski wakeboard and have pulled up to 3 people behind mine with no problem, and i have the little 7.4l volvo.

[noblealloy]

Thsnks! Can you tell me what prop you use and your elevation?

[mikeyt]

Originally Posted by luke7575

I own the Z302 and i ski wakeboard and have pulled up to 3 people behind mine with no problem, and i have the little 7.4l volvo.

All of our Mariahs can tow skiers/wakebarders etc but what effects altitude would have on his boats performance while doing so was what the OP was getting at. Doesn't matter what boat you have, your engine will lose some serious punch if you dont make the necessary changes.

[luke7575]

Ok gotcha sorry bout that I own diesels and I know altitude changes alot didnt knoe it was that big of a problem on gas. But now that I think about it. Its essentialy the same thing different engines

[csterner]

I think Mikey hit the nail on the head. To be more specific about his original question....what specific changes would need to be made to bring a boat from sea level to 6,000 ft elevation. And if those changes are not made, would he be able to pull someone "out of the hole" with the 6.2L engine?


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[Motoxxx43]

I have a similar set up. You are heavier than my Shabah 250 with a 7.4 Bravo 1. I got my boat from 2,200 ft elevation an brought it back to Colorado at 5000 ft. I did not change from the Mirage 19p prop an it runs decent. I don't hit recommended WOT at 4600 but about 4400.
I went down to 3700 ft at Powell a few weeks ago. Ran noticeably better. Out of hole faster an top speed was up about 3-5 mph.

If I were to take my boat to sea level from 5k feet I would personally go from a 19p to a 21p. That's just a ball park. It'd probably be better at a 22p at sea level but I would have to experience it!

That 6.2 (377) is a running machine! It supposedly was designed to replaced the 7.4 (454). It is lighter and produces more HP (310 vs 320). It revs higher as well, 5600, I think. Just a tid bit for you. (I personally liked that option for a motor)

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