1996 50 HP Bigfoot - Rough Idle

[aswetich]

Posted this last year with no replies so thought I would try again.



I have this engine on a pontoon boat and the hour meter indicates 396 Hours. The engine idles a bit rough so I am wondering what I shoud check. Being a 4-stroke I never have rebuild the carbs, should I ? I think this engine is actually a Yamaha powerhead because Mercury did not have a four stroke one ready yet. The engine has some stickers that indidate a valve adjustment spec. Could the valves need adjustment ? The engine starts and runs under power just fine. Being a pontoon it has been run at just above idle for most of the 396 hours. Is 396 hrs a lot ?

Thanks

 

[jimlad]

Re: 1996 50 HP Bigfoot - Rough Idle

yeah rebuild carbs and clean throughly
see if that helps and let us know how you get on

 

[Windykid]

Re: 1996 50 HP Bigfoot - Rough Idle

When was last time it had a tune-up?

 

[aswetich]

Tune Up

Tune Up

Every year I change the Plugs, Fuel Filter, and lower unit oil. I assumed it had electronic ignition so what else would be done in a tune-up ?

 

[Windykid]

Re: 1996 50 HP Bigfoot - Rough Idle

What did the plugs look like?

 

[aswetich]

1996 50 HP Bigfoot - Rough Idle (4 Stroke)

1996 50 HP Bigfoot - Rough Idle (4 Stroke)

They actually looked kind of wet and dark. (All looked the same) I run and repair 2 stroke snowmobiles and it looked like a two stroke running rich.

 

[Windykid]

Re: 1996 50 HP Bigfoot - Rough Idle

Maybe sticking float?

Rings sticking?

Try some see foam?

 

[aswetich]

Re: 1996 50 HP Bigfoot - Rough Idle

I looked at the SeaFoam web site. Do I just pour it in the tank or is there some way to pour it in all four carbs ?

 

[Windykid]

Re: 1996 50 HP Bigfoot - Rough Idle

Do a search on this site, It has all the directions. Good Luck!