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High altitude carburetor tuning

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iwinn

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"I have a 1988 200 horizon fou

"I have a 1988 200 horizon four winns with a gm 5.0 liter engine and cobra outdrive, we brought this boat over from the east coast at 0 elevation to park city,ut at 6,000 elevation and the boat is just running like dog, no hole shot etc. I changed props to a 14 pitch,and 14.5 diameter, 4 blade, power tech, to no avail.
! just wanted to know if anyone has found a good jet combo for this altitude or has some profound advice for me on altitude tuning. thanks in advance for the replies

Also i had water in my cylinders and in the oil it was nasty buisness. But thanks to this board i learned to check and fixed the exhaust manifold/elbow seal and that seems to have stopped it for the moment and she's running lots better. I just hope it isn't leaking from multiple places."
 
What prop did you have before?

What prop did you have before? What drive system is on the boat?
 
"old prop was the same diamete

"old prop was the same diameter and 19 pitch, and the drive system is a cobra 800 series i think?
i just ordered a jet kit for the carb i'm planning to drop the main jets down 3 sizes hopefully that will lean it out a bit."
 
"seems there is a timing chang

"seems there is a timing change too. don't just guess at it. check with local shop. I'm kinda fuzzy on this, and definately sea level guy, but I think I remember something from school, or maybe a service bulletin."
 
You are close on the jets. I w

You are close on the jets. I would have tried 2 down first but 3 should be ok. Add 1/2 degree of timing for every 1000ft. Do not go past 12. What rpm is it turning now? I think the max rpm is 4600 but double check that. When it leans out it should gain some rpm. Keep in mind it will never have the power you had at sea level. So don't be expecting the same speed as you had or to be able to pop a skier out as it did. Best of luck.
 
"ok I'll try 2 down first

"ok I'll try 2 down first on the jets from stock then and play with it from there.i think you guys are spot on with the timing that's a good idea, i've never messed with it before but i just bought a timing light gun so that will be fun to try out. I haven't run the boat yet without water in the cylinders this year, but water logged it was approx. 3800 WOT. Just tested the compression and i'm all over the place from 155 to 120, min should be no less than 116 so i guess i'll just run it and get the 5.7 later when it blows!
thanks for the replies everyone"
 
What are you talking about wit

What are you talking about with the water in the cylinders?
 
"there was water in every cyli

"there was water in every cylinder per, my first post. I haven't taken the boat out again since the exhaust/riser gasket seal has been fixed, so i don't know the true WOT yet."
 
"ok went down 3 sizes on the j

"ok went down 3 sizes on the jets (plugs changed to a great light brown color), advanced the timing to 5. The boat is pulling hard, i'm way stoked. It hardly pushes any water at all to get on plane in 2 seconds. The prop is perfect the boat is turning 4400 wot. Thanks for the info,
best"
 
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