2bbl Mercarb adjustment...black smoke :(

[mia9516]

I have a 4.3L MerCruiser Alpha One with a 2bbl Mercarb. I've had some issues with idling that I've corrected. Currently, the idle is set to 700rpm in neutral.

Now the problem plaguing me is black smoke coming from the exhaust while the engine is running? Is it possible to adjust the fuel mixture, accurately, in my driveway? Or is this something that needs to be done in the water? I do know that I'm running rich by the tell-tale black soot on the spark plug porcelain. And I also know that to lean out the mixture, one must turn the needle in clockwise. I'm just wondering if I'd be better suited by waiting until I can my boat in the water. Thanks in advance.

Milton

 

[a70eliminator]

Re: 2bbl Mercarb adjustment...black smoke

You can trim the air fuel mixture screws while on muffs in your driveway, then when you get the motor exhaust underwater check it again.

 

[John_S]

Re: 2bbl Mercarb adjustment...black smoke

I have a 4.3L MerCruiser Alpha One with a 2bbl Mercarb. I've had some issues with idling that I've corrected. Currently, the idle is set to 700rpm in neutral.

Now the problem plaguing me is black smoke coming from the exhaust while the engine is running? Is it possible to adjust the fuel mixture, accurately, in my driveway? Or is this something that needs to be done in the water? I do know that I'm running rich by the tell-tale black soot on the spark plug porcelain. And I also know that to lean out the mixture, one must turn the needle in clockwise. I'm just wondering if I'd be better suited by waiting until I can my boat in the water. Thanks in advance.

Milton

You can adjust idle mixture while on the muffs. It sounds like it is way out. Then, you can just do final adjustments in the water. Prior to T5 (you didn't mention what you have) idle speed has to be set with boat in water and in gear. Whenever adjusting idle speed it is a back and forth adjustment of idle speed and idle mixture.

PS: Make sure there is not any fuel in mechanical fuel pump site line (if you have one) and fuel is not dribbling down the barrels. While it might be still idling ok, there are other issues to address before hitting the water.

 

[HT32BSX115]

Re: 2bbl Mercarb adjustment...black smoke

Howdy,


Make sure the choke plate is all the way open when you do the adjustment too.

 

[mia9516]

Re: 2bbl Mercarb adjustment...black smoke

You can adjust idle mixture while on the muffs. It sounds like it is way out. Then, you can just do final adjustments in the water. Prior to T5 (you didn't mention what you have) idle speed has to be set with boat in water and in gear. Whenever adjusting idle speed it is a back and forth adjustment of idle speed and idle mixture.

My engine is an '89 4.3L Merc. I know what you mean about adjusting idle in the water and in gear. I made the mistake of setting the idle to 700rpm in the driveway and then the engine would stall once i'd put it in gear in the water. So I thought "Set it to 1000rpm in the driveway and i should be good". Bad idea. When shifting into forward and reverse it pretty much banged into gear everytime. I'm lucky the prop shaft is still in one piece. I learned that lesson already.

 

[jtmarten]

Re: 2bbl Mercarb adjustment...black smoke

Flame arrestor clean??

 

[mia9516]

Re: 2bbl Mercarb adjustment...black smoke

Flame arrestor clean??

It's kind of sooty in some parts. It could use a cleaning though. I've read about using soapy water, soaking in gasoline, spraying with carb cleaner or brake cleaner. What's the best method with less hassle?