1989 Mercury "classic fifty" 45hp

Engine Idles well, and makes good power, but runs rough (sounds like a misfire) at around half throttle, and also above 95% throttle. The misfire is related to throttle amount not RPM. Doesn't seem to be a fuel issue as I can run it just below WOT for extended periods of time. Plugs are new. I haven't looked much into the electrical system yet and was just wondering the best place to start.

Comments for 1989 Mercury "classic fifty" 45hp

Average Rating starstarstarstarstar

Click here to add your own comments

May 27, 2023
Rating
starstarstarstarstar 		1989 Mercury "classic fifty" 45hp
by: Anonymous

The place to start is to do a compression check, and spark check. Then make sure you have a good fuel supply. Use a remote tank different from what you use all the time. Pull the fuel line after the pump and make sure you have about 5 lbs pressure and good fuel flow to the carbs. If that checks out, then rebuild carbs. That should take care of the problem. If not, you know the fuel system is good, then look at electronics. I have an interment that I can check voltage at the coils and plugs. but try unplugging each plug one at a time to see if you can isolate a cylinder that is giving you the problem. if you can then check electronics to that cylinder. If not then your looking at spark box. But I think you will find your problem before that.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Mercury Forum.