Mercruiser 140 stalls/coughs while accelerating

Hi All,

I have a 1980 17' galaxie with a 140 Mercruiser, I am having a little problem.

While on the muffs, the engine idles quietly and smooth around 500 rpms or so, accelerates great, shifts into forward and reverse smoothly and accelerates easily.

While on the lake, the engine idles great with no problems, shifts into gear and runs great under 1000rpms. But the second I go to try and open the throttle up above 1500rpms the engine coughs, tries to stall and even got a backfire today. If I mess with the throttle enough and slowly try and push the engine it will eventually accelerate up to 3000 rpms and plane out really nicely.

Does anyone know what might be keeping it from accelerating? Maybe a vacuum problem? I really appreciate any help you guys can offer!

Re: Mercruiser 140 stalls/coughs while accelerating

worn accelerator pump in the carb. My 120 does the same thing.

Re: Mercruiser 140 stalls/coughs while accelerating

Thank you! Would I be able to buy an accelerator pump from a local auto parts store, or would I need to go to a marine dealer to buy a special mercruiser accelerator pump?

Re: Mercruiser 140 stalls/coughs while accelerating

Mine did the same when I hit the secondaries. After trying many funsuccessful fix atempts turned out it was the anti-siphon value sticking, not fully opening

Re: Mercruiser 140 stalls/coughs while accelerating

I just fixed my sons 130 hp 4cyln carb the other day. His had a 2barrel carb. When you look down into carb make sure BOTH pump jets are squirting a solid fuel stream into each barrel! if not you may have a clog
Bob

Re: Mercruiser 140 stalls/coughs while accelerating

The idles ok but won't go under throttle without major power loss and coughing/sputtering certainly sounds like a carb issue and would be a good first place to look. Someone suggested a worn accellerator pump and thats a possibility. The rubber cup at the end of the pump rod wears and deteriorates with age, use and exposure to fuel and eventually fails. A clogged jet, powervalve, or venturi cluster can all cause different fuel problems upon accelleration and with ethanol blends now those problems are getting more common. If you are suspecting that you are having issues with your carb that are internal and unidentified the best thing to do is get the full rebuild kit, bring you carb home with you, and get out the manual for it. A full rebuild on this particular 2 barrel should take you no more than 4 hours even if you have never done it before. It requires nothing more than common tools, and the results are very good. A kit is under 100 bux and it sure beats paying 400-500 for a new carb or wasting half your summer fixing your carb 6 differnt times.