Thread: rough start

Hey all gotta a question for ya. I have an 02 40hp merc. Just the last few trips I have had trouble getting the engine warmed up. Starts fine but then as I give it some throttle it dies. So I have to let it basically idle real rough for a min or two and then it will smooth out. Once I get it going it has been fine the rest of the day. Do you think I just need the carbs cleaned, new primer bulb? Any ideas? Thanks

First thing I would do is put a can of seafoam in your fuel. Many times that will solve your problem...its not a miracle worker but its about as close as I've seen...lol.

I would also pull the plugs...check them. If they are really black try cleaning them. With an emory cloth...then blow them out. Try this at the ramp and see if the engine improves...you might have gotten a bad batch of gas.

Have you changed your oil?? Brand I mean??

Do you idle alot or do you get out and run each time you are out?? If a two stroke idles a whole lot eventually you'll run into this due to carbon build up.

May just need to change your plugs.

Check the fuel filter..make sure it isn't clogged up or flowing slowly. May just change it anyways to be sure.

If it still does it...pull the cowling off at home on muffs and at night in the dark. Watch when you first start it while its idling rough and see if you see any sparks jumping around anywhere...sometimes its something like a plug wire that as it warms up the "pinhole" in the wire seals it self off as the wire warms up and expands. When it gets cold outside this can get worse. Just some things you can check that really won't cost you much before doing anything that will cost a bit.

When you start it and its running rough try to pump the bulb...not hard..just see if its firm...if its firm you don't have a problem there. If it will pump you may need a bulb or even a fuel pump rebuild.

If none of these things show you anything or help....I'd pull the carbs and rebuild them. You may just have some trash in the idle jets...but there again it shouldn't just do it when its cold. Although its possible. Nearly anything is possible with an outboard...lol.

Just some food for thought.

May try hitting the choke/enricher while its warming up and see if that helps.

read the post again. Take that gas and run it through the weedeater or something...sounds like you got some bad gas and she doesn't want to burn it till she warms up. Put some seafoam in the next tank. A full can will NOT hurt...ecspecially if you've never run it through there before. Will really make a difference.

thanks for the tips. I use some fuel stablizer with each tank, but It has been prolly 2 months since I have filled the tank so I cant remember 100% that I added it then. I have used the same quicksilver oil since I have had the boat.

I will check on some of this hopefully this weekend. Thanks for the tips

I'm a recent seafoam convert myself. Had the same problems you described on my 25hp Mariner. Took the cover off night before going and squirted Deep Creep into the carb throat and put seafoam in fuel mixture. Ran like a new motor.