Need help with carb adjustments and throttle settings.

[starkyb]

I have a 75 horse mariner that I had some work done on it. When I got it back the motor was idling at 2000+ rpms. I can get it to idle at a more reasonable rpm by adjusting the screws on the side of my 3 carbs but have trouble keeping the motor running when I put it in gear. I made some adjustments to the throttle positions as well as the idle screw and max spark screw. The motor runs perfectly after getting it up past about 1700 rpms. I'm just having problems in the low rpm range. Anybody out there have any suggestions?

 

[NWVintage]

Re: Need help with carb adjustments and throttle settings.

Without anymore information, it sounds like you adjusted your idle air screws to get the idle down. Adjust them back to where they were. Adjust your idle stop screw and (if necessary) your throttle cable to decrease the idle. Adjust the idle air screws on the carbs on at a time to MAXIMIZE idle speed and smoothness. Reduce idle via stop screw and throttle cable until it's at a good speed. Once in the water, give it some gas and, if it doesn't feel like it will take the hole shot, adjust the idle air screw out about 1/4 turn further (do this evenly between carbs). Try the hole shot again. If that's not enough, another 1/4 turn...

 

[NWVintage]

Re: Need help with carb adjustments and throttle settings.

Also, put the max spark advance back where it was unless you actually know it was off. That wouldn't have any effect whatsoever on idling.

 

[CharlieB]

Re: Need help with carb adjustments and throttle settings.

Do you have a FACTORY service manual?

If not, check these links to see if yours is available for download.

http://1manual.com/Mercury manuals/Service_Manual_Index.html

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

Study the section on Carbs, and ignition timing, specifically, adjusting the carb linkage and setting timing. Once that is done then follow the instructions on setting idle mixture and idle speed.