My 50 horse mercury's got a cough!

[Pool_Eleven]

When in idle it will idle normally then all the sudden it lets out a big cough. Then it goes back to idling normally for about 10 seconds and then lets out another big cough. Sometimes the cough is big enough to kill the motor. Its fine when it runs wide open or even at a slower pace, basically anything above idle is ok. Any ideas what the problem may be?

[Gordie]

Try some seafoam in the gas sounds like it could be dirt in the carb or junk built up from sitting all winter.

if it doesn't go away you may need to rebuild the carbs.

I would check the plugs also.

[jentz]

The idle passage it restricted,Try any carb cleaner in the fuel and open each idle needle 1/8 turn.Then run it it idle often.Remember the 1/8 if the carb cleaner works you'll have to reset it back.you dont mention year or model, I assume it has two carbs.

[Pool_Eleven]

Sounds good guys. Ill give it a try. Thanks

[fish_eat_sleep]

Had an optimax do that after trolling or idling for long periods of time. All i had to do was run at 75%-100% throttle for about 20 minutes and it went away. That was a DI model so not sure if its similar. after the engine warmed up to operating temp everything was fine. Figured it was the short trips and idling..

[LindellProStaf]

I have a 97' Merc 60 hp. It was doing the same thing and took a lot of choking to keep running at cold idle. Turned the screws in and counted the turns then out to same spot plus the 1/8 turn you said to do. Put in Seafoam too. Absolutely worked like a charm. Starts and idles much better. Thanks for the advice...