altitude affects carburation

[h205150]

I have a 1987 OMC cobra that is installed in a Winner 1750 Escape.I will be using the boat at a higher altitude than we normally boat,the diffrence is about 5300 ft.I relize that I am going to lose performance and some of it can be made up with the prop pitch, does anyone have thoughts or input on the carburation for this altitude.

 

[HT32BSX115]

Re: altitude affects carburation

altitude affects carburation

Indirectly true!

Altitude affects what you should do if you're going to run up high for a long time. You could replace the jets in the carb,

According to:

Holley carburetors, manifolds & fuel injection: how to select, install, tune, repair, and modify Holley fuel sytem components for street and racing use
By Mike Urich, Bill Fisher

To run a Holley at 5000 ft MSL, you would need to reduce the jet size by "2 sizes"

Since you're also not going to develop full power you would also need to put a lower pitch prop on the drive. I don't have my 1987 OMC service manual anymore but I seem to remember OMC suggesting how many inches(pitch) to change. Someone should jump in here with a suggested amount to drop your pitch.


Good luck,



Rick

 

[flargin]

Re: altitude affects carburation

welcome to the world of high altitude... less power, smaller props, slower boating...

At least we don't need to worry about all the problems associated with running in salt water

 

[HT32BSX115]

Re: altitude affects carburation

Well, all you gotta do is install a supercharger then all is well!! It only takes money!

 

[jaxnjil]

Re: altitude affects carburation

I have a 1987 OMC cobra that is installed in a Winner 1750 Escape.I will be using the boat at a higher altitude than we normally boat,the diffrence is about 5300 ft.I relize that I am going to lose performance and some of it can be made up with the prop pitch, does anyone have thoughts or input on the carburation for this altitude.

i boat any where from 1100ft to 7500ft. mostly at 6600'

when looking for jetting recomendations for my mercruiser i couldnt find any. all i could find is mercruiser recomends changing prop pitch to stay in WOT specs. this is what we use
7500'+ 17 or 15 pitch 3 blade aluminum
6600' 19 pitch SS 3 blade or 4 blade aluminum
3600'- 21 .................................................

 

[h205150]

Re: altitude affects carburation

Thank you all for the inputs and information that you have passed on it will help me in the future