Outboard Motor Running Rough at Idle

[cannonball]

Okay so as some of y'all know i recently bought a pontoon. Its got a 98 50hp johnson 2 cyl 2 stroke. It runs great at everything other than idle. I don't have a tach but i'd say at everything over 2000 rpm. Runs great wide open. When its at idle it is only running on one cylinder. I found that out when i pulled the plug wires. I am getting spark to both cylinders because the sucker shocked me both times. But I'm not sure how strong of a shock. I also replaced both plugs

On the cylinder that isn't running at idle, I think the carburetor is the issue. When i pulled off the flame arrestor there was fuel puked up all around the carburetor. And on the top of the carb where the primer goes in it had a pretty good residue of gas. around it. I cleaned it, and saw some more starting to squeeze out. I'm by no means an expert on these things so any thoughts will help.

 

[cannonball]

Link to the carburetor that is on it

http://www.boats.net/parts/search/BRP/JOHNSON/1998/J50TSLECC/CARBURETOR/parts.html

It is leaking under the cover (number 2) and onto gasket 5.

 

[matth_85]

Maybe my brother will see this and chime in. He's pretty sharp on outboards

 

[97TJGUZZY]

Link to the carburetor that is on it

http://www.boats.net/parts/search/BRP/JOHNSON/1998/J50TSLECC/CARBURETOR/parts.html

It is leaking under the cover (number 2) and onto gasket 5.

time for new gasket 5?


open your wallet and just dump it out on the water and grab a paddle:

 

[matth_85]

B.O.A.T. Bust out another thousand

 

[cannonball]

haha the only thing i will ever even possibly spend a grand on the boat is seats. The top cyl is the one that does great at idle, and the bottom is the one that needs help. So i think i'm gonna swap the carbs between the top and bottom cylinders to see what is going to happen.

 

[MountainGoat]

haha the only thing i will ever even possibly spend a grand on the boat is seats. The top cyl is the one that does great at idle, and the bottom is the one that needs help. So i think i'm gonna swap the carbs between the top and bottom cylinders to see what is going to happen.

Usually the carbs are in a designated position. Sounds like the carb needles/seats need a good cleaning or a new intake gasket and reeds. Also check the specs for the number of turns in/out on the air/idle mixture which looks to be on top plate of your carb in that diagram if it has it. That gasket leaking is not good either because it could cause a lean running cyl.

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[GREASEMONKEY]

I had a similar issue on my old Mercury 50. The carbs needed to be rebuilt, and the linkage between them was shot.
I work with a guy that retired from Marine motor work, I can get his info if you want. He fixed up my old motor for around $120. Not bad for a tune up, rebuild 2 carbs, replace linkage.

 

[cannonball]

Usually the carbs are in a designated position. Sounds like the carb needles/seats need a good cleaning or a new intake gasket and reeds. Also check the specs for the number of turns in/out on the air/idle mixture which looks to be on top plate of your carb in that diagram if it has it. That gasket leaking is not good either because it could cause a lean running cyl.

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so you'd say don't switch the carbs? both carbs are completely identical. and i figured that gasket leaking was what was making it start running lean. I've messed with the idle air mixture. Set it at 2.5 turns out. That is where it ran the best everywhere. I feel like the float is the issue or the idle gas mixture is messed up.

I had a similar issue on my old Mercury 50. The carbs needed to be rebuilt, and the linkage between them was shot.
I work with a guy that retired from Marine motor work, I can get his info if you want. He fixed up my old motor for around $120. Not bad for a tune up, rebuild 2 carbs, replace linkage.

I'm going to try and tackle this myself so i don't have to spend money on it. But if i can't i'll call up that guy. No idle in gear is a full on bitch.

 

[MountainGoat]

Most engines I have experience with are 3 cyl Yamaha's and the carbs are all different. I would at least check the needles/seats and jets. Particularly your low idle jet. Pull the lower carb bowl and look for the ethanol gunk in it.

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[WeRideNTruX]

Worked on a guys mercury at work one time that had a similar prob & from that limited experience I'm gonna jump on the clean carb/ new gasket band wagon here

 

[GREASEMONKEY]

Or you could just pony up, and buy a yamaha 4stroke efi.
I change my oil on time, and plugs after 6yrs. Runs on pump gas, and moves faster than a $10 hooker on pay Friday!

 

[bluezj]

2 cans of sea foam in 6 gals of non ethanol fixed my 50hp motor.

 

[cannonball]

2 cans of sea foam in 6 gals of non ethanol fixed my 50hp motor.

Lol this sounds like its going to be my first plan of action. I'm sure this old 2 stroke could use a little cleaning. Who makes yours?

Thanks for all of the replies. I will keep y'all updated on what's happening.

 

[bluezj]

Lol this sounds like its going to be my first plan of action. I'm sure this old 2 stroke could use a little cleaning. Who makes yours?

Thanks for all of the replies. I will keep y'all updated on what's happening.

Mine is a '99 Mercury.

 

[YJeeper]

i had a buddy with the exact same motor on his toon' having the same issue.... We bought two carb rebild kits and went threw them and it fixed his... Its atleast a good start on a 15yr old motor..

 

[cannonball]

i had a buddy with the exact same motor on his toon' having the same issue.... We bought two carb rebild kits and went threw them and it fixed his... Its atleast a good start on a 15yr old motor..

sounds good. that's what i'm thinking it is, but i'm going to try and run some seafoam through it. I feel like something is just gunking it up cause the carbs look somewhat recently rebuilt.

 

[MountainGoat]

Don't use ethanol fuel. Not even with sea foam or stabil. It will gunk up your carbs and the only way to get it out is pull the carbs down. The sea foam might make a fix for a while until some more build up brakes loose and clogs up a jet again.

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[james]

Don't use ethanol fuel. Not even with sea foam or stabil. It will gunk up your carbs and the only way to get it out is pull the carbs down. The sea foam might make a fix for a while until some more build up brakes loose and clogs up a jet again.

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x2

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[cannonball]

Don't use ethanol fuel. Not even with sea foam or stabil. It will gunk up your carbs and the only way to get it out is pull the carbs down. The sea foam might make a fix for a while until some more build up brakes loose and clogs up a jet again.

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Oh yeah I know. I haven't had ethanol fuel In any of my now 5 marine engines. Sit down Jet ski, old boat, new boat, stand up jet ski and pontoon. Ethanol fuel gunks everything up. But I'm thinking the guy before me ran ethanol fuel in it all the time.