78 140 horse evinrude bogs down after running

[gcman49]

I have a "78" 140 horse evinrude that is starting to progressively have problems attaining higher rpms. The summer started and the engine ran great. I could run, shut down, start up and go. now after running for awhile and shutting the engine off I am unable to throttle up without the engine bogging up and shutting down. It starts up fine but when I raise the warm up lever to full throttle I am only able to develop around 1200 rpm's. It will run for awhile and then slowly the rpm's will start to increase to about 5500 rpm's. but it takes about 5 minutes. If I shift into forward and give it gas it pukes and dies unless I work it like a gas peddle, give it gas, back off, give it gas....etc. after about 5 or 10 minutes it finally starts running and I can run wide open. I have changed plugs and ignition coils, by the way I have 77 140 horse coils, I don't know if the power heads were changed, and checked the all the voltages and everything seems ok. It seems to get plenty of gas, my fuel mix is good, I disconnect the gas line and run the gas out of the float in the winter. If I leave it in neutral and work the carburetor throttle manually it runs good. I can raise the warm up lever and work the carb. throttle manually it runs up to 5500rpms and the spark advance works like it should. I can put it in gear and work the carb. throttle and the rpm's increase. If I let it sit overnight it runs good again in the morning until it warms up. Like I said earlier it is getting worse, the more I run the harder it is to get up to speed. Is there anybody that can help? Thanks

 

[sho305]

Re: 78 140 horse evinrude bogs down after running

If it bogs and is not missing that really sounds like the classic lean condition. Check the plugs for a light color after running it. Lean can damage the engine as it burns hot and gets little oil if premix. Try hitting the choke a little and see if it helps breifly. Check the simple stuff first like your fuel tank vent to make sure it is not starving it, or if a hose is kinked, or bad pumps. My 150 had rubber bits in the pumps and filters from a bad bulb on the hose.<br /><br />Most ignition parts die after getting hot. I have had the condenser go bad and leak power when warm, or a pickup will do that too and still run. If the plugs are wet then look at the ignition. Try a tuneup first if needed.

 

[gcman49]

Re: 78 140 horse evinrude bogs down after running

The plugs seem to get a lot of oil build up on them and I have cleaned the fuel filter. I seem to get plenty of gas. The engine seems to run cold. i can touch it, even after running for an hour. Like I said after it starts running I have no problem until I shut it down for awhile, like maybe 5 minutes. Them I have to go through the whole routine again. It just is getting worse. I'm going to rebuild the carb, hopefully tonight, and see what happens. I'll check the breather on the gas tank