4.3l mercruiser stahl at idle

[Adk1]

So did my maiden voyage on my home lake today. Yesterday changed oil, installed new plugs and ran engine. Everything seemed fine but didn't idle well. Has half a tank left in from last year. Used marine stabil ethanol treatment and sea foamed when put away for winter, filled up tank today used more ethanol treatment. Launched. Engine starts no issues. Idles rough and will stall without throttle. Drove a few miles at least. Tried to setup for a troll, engine running rough at trolling speed. Pulled lines and ran for a good 10 miles on plane, no issues. Setup for a troll,again, engine ran ok bit not great at a trolling speed. Stalled out a few times. Need to give it throttle. Ran back to the launch. Stalled coming into the dock. Chewed through a quarter tank of gas on an 85 gallon tank. Thoughts?

[lost a lure]

Clean the carburetor

[Xxx]

I had same issue last year, changed fuel filter (water separator) worked better but not great, pulled the bowl off the carb. 3/4 full of water, wiped the bowl clean bolted her back on problem solved. Have to do my JD tractor twice a year since the corn juice been added to the fuel. Hope you figure it out!!

[Has Been]

If you don't have an Oil filter type fuel /water seprator, Might be a good idea to get one w/ the lousy gas we get these days.

 

Half tank stored means a lot of air space for condensation on walls of inside your tank all winter.

[Adk1]

Yes there is a water separator, hadent been changed in 2 years since I bought the boat. Damn thing is impossible to get off. I guess I will have to figure out how to clean the bowl, no clue there. I fog the piss out of the carb with sea foam when she is put to bed for the winter

[TileMan Dan]

Definitely change that water separator filter. Also add the ethanol gas stabilizer on fill ups. Might want to consider using premium gas in boat if your not running it regularly. This ethanol does nothing but bad things for engines. At seasons end you should try and get tank empty as possible for winter storage. Also having problems with it in all my lawn equipment as it breaking down fuel lines and primer bulbs

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[Adk1]

I do use the marine ethanol at every fillip and during storage. Thanks

[rlconverse]

What yr is your engine? If its older check the point. Sometimes they tend to get corosion on the contacts from setting over the winter

[Adk1]

ITs a 1991 4.3L carburated Mercruiser.

[Xxx]

Definitely change that water separator filter. Also add the ethanol gas stabilizer on fill ups. Might want to consider using premium gas in boat if your not running it regularly. This ethanol does nothing but bad things for engines. At seasons end you should try and get tank empty as possible for winter storage. Also having problems with it in all my lawn equipment as it breaking down fuel lines and primer bulbs

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[rustyrat]

Change the water separator and check the carb. Mine did that and all it needed was a carb rebuild. Sounds exactly what happened to me.

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[lineman49]

  Change the separator, put in fresh premium gas , & K-100 gas treatment .  Also as suggested check contacts inside distributor .on the cap itself.

[Adk1]

any links to rebuilding a carb? no clue here.

[rustyrat]

It's not that expensive to have it professionally rebuilt. I think.it was 150 bucks including the kit. The reason I think.it's the carb and not gas is that it runs fine other than idle. I've had bad gas and it will run crappy at any speed.

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[Adk1]

I am sure you are correct. Gonna replace the water Seperator filter Sunday and fire her up,and see what happens at idle

[thumbburn]

get the carb done as well......do it all one time.....

[TileMan Dan]

Hopefully you can get away with just a filter change but just be prepared for the carb rebuild. This ethanol is just a bad b$$$ job.

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[lakebound88]

Water separator and carb rebuild... everyone above is dead on...

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[jigstick]

Dont get me wrong, i love Seafoam, and use it in every vehicle i have.  But sometimes it does cause rough idling.  In my bo at, it takes 32oz to treat the entire tank, which I believe is 42 gallons or so.  Where I fill up with gas, Stabil is already added.  Having 32oz of Seafom and a tank full of Stabil as well is ALOT of alcohol to have mixed in the gas.  It MAY be that.  Before you go for a carb rebuild I would run as much as that Seafoam treated gas out of the tank as you could.  remember, that Seafoam is dissolving a bunch of dirty buildup in the engine, cylinders, AND carb.  You have have just dislodged a bunch of **** and it needs burned through.  Just an Idea.  Certainly a Carb rebuild and fuel/water seperator change isnt going to hurt, and it should be done every few years or so.  But try getting some fresh gas in there.

 

Seafoam caused rough idling in my tractors and boat before when a full treatment was added.  nothing wrong with that, its doing its job.  Cleaning everything up.  Once I burned the treatment through, and added fresh gas, it ran great.

[Adk1]

I used the sear om only to fog the carb when I put it away and it wasent added to my fuel tank

[Adk1]

Ok so I replaced the water/fuel Seperator filter and it is still stalling at idle and at a troll, really knocking allot under 1000 rpm but once I give it enough throttle and over 1000 rpm it runs smooth and fine. Thoughts?

[lost a lure]

Rebuild the carburetor! Or at least open it up and clean it.

[Adk1]

Rebuild the carburetor! Or at least open it up and clean it.

yeah I don't know how to do that so I guess I will be bringing it to our local mercruiser marina....

[lost a lure]

Look it up on youtube

[Xxx]

Rebuilding the carb. sounds and appears scary, but if you have any mechanical ability you can do it

yourself. A very clean area is a must!! I personally think you have a bad batch of fuel, and the above post is dead on by saying run that fuel out first, then if there is no improvement I would look into the carb,