1994 120hp Johnson running funny

I have a 1994 Johnson 120. It ran ok in early Aug 05, but after Katrina it sat up until a couple of weeks ago. I drained the fuel tank mainly because I was changing the ascending unit for the fuel gage. I found that the fuel line was in bad shape so I replaced it from the tank to the engine. I then filled the tank up with fresh gas and charged the batteries. I took a little while to start, but it did start and ran fine. I added some carb cleaner once it started and ran it for a while before taking it out. When I did finally take it out it started better than it ever had, and we ran about 100 miles mostly at speed with some no wake zones. Towards the end it started to die at idle while going through no wake zones. I didn’t think much of it at the time; I thought the idol speed may be to low. Last summer it was common for the engine to limit RPMs when it was in gear until the engine warmed up. It didn’t do it every time but more often than not. I just thought it wasn’t warm yet. Last weekend I took it out again and more problems have started. It did the RPM limit for a while but like usual it eventually allowed the engine to rev up and ran ok. When we stopped to fish the engine started to run rough at idol. As the day went on its low speed performance got worse. By the time we put the boat back on the trailer we could barely keep it running at idol, and when it was running, it was missing. I pulled the plugs and all four were wet fouled, but did not have any resistance when tested with and OHM meter. The plug wires checked out ok as well. I am sure it needs a new water pump as I have had the boat for a few years now and have not changed it. The water pump obviously is getting water through the engine. I tested the alarm horn and it works so I do not think it is overheating. Where do I start and how do I check it? Any advice is appreciated

Re: 1994 120hp Johnson running funny

Hi Morgan and welcome aboard!<br /><br />Start with the basics. Get a comprssion test on each cylinder just to make sure there is nothing hidden and we cover all the bases.<br /><br />Check the spark to each cylinder. They should be consistant and jump a 1/2" gap with a hot lighting like spark.<br /><br />Check your fuel lines. Make sure all are in good shape and are plyable and have a firm grip on their connections. Pump up the primer bulb and keep pressure on the fuel system and inspect for any leak.<br /><br />Setting for a year, it's possible one or carbs could be fouled and need a cleaning. But let's go with the above first and see what you find...especially in the spark area. If you can, run the engine on the water until the problem occurs. Then check for spark...a timing light works well for this.

Re: 1994 120hp Johnson running funny

Thank you very much. We will start there and hopefully it is something simple so we can still go fishing this weekend. Hate to have to cancel the trip.

Re: 1994 120hp Johnson running funny

Compression test showed 125 psi to 130 psi in all four cylinders. All four cyliders passed the .5-inch gap spark test. The entire fuel line is new hose and I can pressure it up with the primer bulb and no leaks appear. <br /><br />I pulled the cover off of the carburetors and sprayed carb cleaner directly into the float valves and let it run for a while. After I did that the #4 cylinder started to backfire (lowest cylinder on port side, I think it is #4). I pulled the plugs again and that plug was burnt and the other three were a little wet but not as bad as before. I cleaned and gapped the plugs and then installed them in different cylinders and re ran the engine. The same cylinder started to burn the plug again, but no backfire was apparent. While I had the plugs out I looked into the cylinders and the piston heads looked pretty gunked up. Is there a way to clean them without tearing the engine down?<br />I am going to try to pull the pulse limiter and clean it, I am going to put a timing light on it and see if that turns anything up.