High altitude carburetor
 

Hello, my name is Caleb. I am new to this site so bear with me. I have a 1986 sunbird that is new to me. I need to rebuild the carburetor because it is running poorly and the previous owner told me that I need to get it rejected for high altitude as I live at 8200. Does anybody know how or what to buy for this? I am seriously at a loss and cannot find any information if anyone could send a link that would be great. the drive is an alpha one GEN one. It’s not letting me upload the photo, so here is some technical information. Serial number 867810, model MCM 140, 1986 Mercruiser.

Have you tried finding a local shop that has experience with jetting for your altitude? 8200 ft. is up there. I think you have to post about 10 times before you can post a photo.

Welcome to OSO, post a few more times and you will be able to upload pictures. They can be meaningless, but if entertaining it's appreciated.
You will find excellent support on this site, however your location is unique so the number of members that can confidently provide support is limited.

I'm assuming that you have the Mercruiser quadrajet carb on it??
Im not sure about those and im sure someone else will chime in that does know more...but i do remember from reading something on Holley's a while ago that they recommend dropping one jet size for every 2000' in elevation. So for you being at 8000+ you would go down 4 jet sizes and start dialing in from there...
Actually i went and got lucky and found the article.... https://www.holley.com/blog/post/how...high_altitude/
Im sure there's probably something on the internet on the Quads as well....

Probably not a Quad on a 140. Whatever the carb, I would look at Mike's Carburetors web site in Washington or Oregon, I cannot remember. He has individual parts for a LOT of carbs. His rebuild kits are top notch too.

What a phenomenal article! Thanks for posting that!

Holy crap thats 2000 ft above Tahoe, they got lakes in the Swiss Alps......:D

There is a service bulletin i linked years back, if you do a search, from Mercruiser for jetting most of the black motors for different altitudes. I believe it included part #’s too.

Since engines lose Approx 3% hp for every 1k feet elevation - assuming tune is correct. they also provide suggestions on regearing the outdrive. Sorry to say your engine makes little hp to begin with, so very little after accounting for elevation. 24% less at 8k feet ! You’ll have 104.6hp if in perfect health and tune.