150 Merc idling rough but running great...ideas

[pathfinder]

My engine seems like its running a little rough on idle but when I give her gas she runs fine. I'm thinking it may be a spark plug. Any ideas?

 

[ljm336]

Could be a bad primer bulb, my 115hp merc did the same thing

 

[pathfinder]

Difficult fix?

 

[ljm336]

No its simple, sometimes the just wear out. Here is a link for instalation. http://www.ehow.com/how_7761365_replace-outboard-motor-inboard-tank.html

 

[bluewingjb]

Hey pathfinder what year is your Merc?? How long has it been since you changed plugs? See if you can get any input from James Perry, he goes by wrenchin2 on here, he is OUTSTANDING with Mercs... If its been a while since you changed the plugs I would start there and also next time you take her out check to see if the primer bulb is firm or not when you squeeze it. In fact if its been a while since you changed that I would do both that and the plugs just to see how things go. I know in my case I usually put new plugs in every other year or so.

 

[Auburnwes]

Yea start with changing the plugs, but you may also try running some Berrymans B12 Chemtool in it.

I traded a 4wheeler to James, and it was sputterin, poppin and ran like crap, put some B12 in, ran it to make sure it was in the fuel system. Then parked it in the garage overnight came out the next morning, fired right up and purred like a kitten!

At $3.20 a can, cant hurt to try! I run it all the time. Make sure you wash out your line with some gas after you pour it in (Its some potent stuff!)

 

[wrechin2]

Plugs could help and so could the B-12 as it may be some light varnish in the idle circuit of the carbs, assuming it is not a EFI 150 but if so then it can help the injectors as well.

Is the only issue you having a rough idle? In or out of gear? A leaking fuel pump diaphram, plugs, dirty carb/fuel injector, stopped up bleeder, bad fuel, ect can cause a rough idle.