1999 johson 40

[twofishy4u]

I bought this 40 johnson new in 2001. I troll a lot. This motor seems to foul out plugs more than it should, it runs fine at wot and at take off. New gas omc oil doesn't matter after an hour or two of trolling and it idles poorly. If i change the plugs its fine for about a month then it happens again. Yes I do run QL78YC's. Is it time to put in NGKs? I had a 1972 18 evinrude same issue put in ngks never happened again.

 

[jegervais]

Re: 1999 johson 40

It sounds like either it's running too rich (carbs need adjusting) or it could be running too cold. An engine which does not run up to designed operating temp (in this case 140 degrees F) cannot efficiently burn the fuel/oil charge in the combustion chamber. This could be what is fouling your plugs.<br /><br />And, if the plugs are fouled, there's a good chance the cylinders/combustion chamber is pretty carboned up. A dose of Engine Tuner to de-carbon the motr would be a good thing to do once the engine operating temp and carb adjustments are checked.<br /><br />-John

 

[twofishy4u]

Re: 1999 johson 40

john these carbs have fixed jets and Im using this motor in 80 degree water and its 90 degrees outside. Yes I run omc cleaner through the gas a few times a year. The plugs never completely foul they just don't allow it to idle well for any period of time.

 

[jegervais]

Re: 1999 johson 40

Hmmm. A 1999 Johnson should have adjustable needles (starboard side of carbs, above throttle shaft). Fixed jets went away (on these models) early 1990's. Can you post model number?<br /><br />Water and ambient temp don't matter unless they are extreme (over 100). I've run plenty of engines in test tanks (water temp 70 to 80) and not got the engine much over 100. Engine operating temp needs to be checked per the factory service manual.<br /><br />Ya gotta' make sure the basics are correct before ya move on.<br /><br />John