New elevation

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CatDaddy240

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Mar 31, 2012
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Recently bought a 2007 Four Winns with a Volvo Penta 5.7 GXI. It had been used at Lake Powel 6000' elevation. I will be running this boat in Arkansas at 400' elevation. Is there any special considerations I should take, or modifications i need to get optimum performance?
Thanks
 
Bondo

Bondo

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Re: New elevation

Ayuh,... Welcome Aboard,.... My guess is, yer gonna need a bigger prop, 'bout 2" more pitch, maybe more...
 
Thalasso

Thalasso

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Re: New elevation

Bond-o said:
Ayuh,... Welcome Aboard,.... My guess is, yer gonna need a bigger prop, 'bout 2" more pitch, maybe more...
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Bond-o. Why would he need a diff. prop ? Isn't the engine is Fuel injected? i would think that elevation shouldn't change the way the boat runs.
 
Don S

Don S

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Re: New elevation

What drive do you have? If the DP, you may need to change gear ratio's. You should have a 1.95:1 for the DP at 400'.
 
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sschefer

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Re: New elevation

Thalasso said:
Bond-o. Why would he need a diff. prop ? Isn't the engine is Fuel injected? i would think that elevation shouldn't change the way the boat runs.
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There's less oxygen at higher elevations and even though the engine has FI it will still not be able to make the power it is capable of at 400'. You prop down by 2 inches in order to reduce the load on the engine and run in the correct RPM range for the motor. It's most critical on two strokes but 4 strokes benefit from a proper setup also. Who knows for sure, it may have never been properly setup and may be just fine now.
 
Don S

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Re: New elevation

CatDaddy240 said:
I am running a F-4 i believe. WHat do you suggest?
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Run the boat and find out if anything needs changed. It may run fine without any changes. You should be getting between 4800 and 5200 rpm (assuming it's a 5.7GXi-H or J), at normal load, and trimmed properly.
 
Thalasso

Thalasso

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Re: New elevation

sschefer said:
There's less oxygen at higher elevations and even though the engine has FI it will still not be able to make the power it is capable of at 400'. You prop down by 2 inches in order to reduce the load on the engine and run in the correct RPM range for the motor. It's most critical on two strokes but 4 strokes benefit from a proper setup also. Who knows for sure, it may have never been properly setup and may be just fine now.
Click to expand...

;););)
 
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CatDaddy240

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Re: New elevation

Thanks guys very interesting. Lots of information, this is a great forum. So I guess I need to find out what is the best dual prop for my area and I might all ready have it. THanks again.
 
Don S

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Re: New elevation

CatDaddy240 said:
So I guess I need to find out what is the best dual prop for my area and I might all ready have it. THanks again.
Click to expand...

No, you need to find out what your WOT rpm is. Not what others get or run or anything else.
 
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fishrdan

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Re: New elevation

CatDaddy240 said:
It had been used at Lake Powel 6000' elevation.
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Lake Powel??? Is that Lake Powell bordering Arizona/Utah? The elevation there is around 3600'.

If you are taking about a different lake, never mind my comments and carry on....
 
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CatDaddy240

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Re: New elevation

I am not near my book right now, out of town working. But I will as soon as I get home. I'm sorry Don, but I am a little slow. What is WOT? Could you help me a little here. THanks, thanks for everything.
 
Tail_Gunner

Tail_Gunner

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Re: New elevation

Don S said:
No, you need to find out what your WOT rpm is. Not what others get or run or anything else.
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The fuel injection system you have now can more than compensate for high altitude...maybe a 1-2 mph change...may burn rich at first thought for a while.
 
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CatDaddy240

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Re: New elevation

My apologies, geography is not my strong point, but I know it is way higher than 400' at Ark.
 
Don S

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Re: New elevation

CatDaddy240 said:
I am not near my book right now, out of town working. But I will as soon as I get home. I'm sorry Don, but I am a little slow. What is WOT? Could you help me a little here. THanks, thanks for everything.
Click to expand...

Sorry about that, It stands for Wide Open Throttle.
 
bruceb58

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Re: New elevation

Its very possible that you won't have to do anything with the prop size depending on if the previous owner propped down or not. When I go to Lake Powell, I use the same prop as I do at sea level.

As Don said, run with the prop set you have to see what RPMs you get at WOT. Prop sets for your drive list out at around $1200 so you only want to change if you absolutely have to.
 
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