Engine runs rough and smokes a little

[BlueVIP]

Engine serial # 0f085957 4.3L v6
the boat ran fine when first got it did oil change and fuel filter change still ran fine. Went to Table rock lake and filled up at Indian Point marina noticed the boat started idling rough and blowing a little smoke like it was running rich. Thought maybe it was the fuel. Ran it all weekend at table rock runs fine when throttled down. Got it home put regular premium in from gas station. It seemed to run a little better but still rough at idle and is smoking a little. Still runs great when throttled more than idle speed. I tried uploading a video of it hooked up to muffs but couldn’t.

 

[Rick Stephens]

This a new to you boat?

Regardless, time to check some things and see what condition the motor is in. Check compression is first. Pull your fuel filter and dump the contents into a clear jar. Must be clear perfect clean fuel or you know what the problem is.

 

[BlueVIP]

I’m going to buy spark plugs for when I do compression test. What are the best plugs to buy for this motor?

 

[Rick Stephens]

I’m going to buy spark plugs for when I do compression test. What are the best plugs to buy for this motor?

Or you can find it here in the manual.

 

[BlueVIP]

Thank you

 

[Bondo]

I’m going to buy spark plugs for when I do compression test. What are the best plugs to buy for this motor?

Ayuh,...... AC Delco, MR43T,....

 

[BlueVIP]

I have not done compression check yet. Tonight I opened the engine hatch and noticed my flame Arrestor was really black and plugged. Could this be why my boat is running rough at idle?

 

[achris]

Engine serial # 0f085957 4.3L v6

That's the transom assembly number, not the engine serial number. http://forums.iboats.com/forum/engi...d-engine-serial-numbers?p=6661415#post6661415

.... and filled up at Indian Point marina ....

That's my red flag....

Marina fuel can not be trusted. They just don't sell enough to ensure it's always fresh. And usually they are the only ones in the area, so pretty much don't care if you get a belly full of bad fuel...

I have not done compression check yet. Tonight I opened the engine hatch and noticed my flame Arrestor was really black and plugged. Could this be why my boat is running rough at idle?

That could also explain it... It's one of the things on the maintenance schedule, annual. Clean flame arrestor...

Chris......

 

[BlueVIP]

What’s the best way to clean flame arrestor. I sprayed with what I had of carb cleaner but it wasn’t near enough. Should I soak it or buy another can of carb cleaner spray then spray out with air compressor?

 

[achris]

I wash them out in petrol. Be careful, do it in a ventilated place, and have a fire extinguisher handy.. Then either let it dry naturally, or blow it out with compressed air.

 

[nola mike]

If you're in the states and can't find petrol, gas works as well.

 

[Rick Stephens]

After all the treating of symptoms, like smoking and oil carbon fouling of flame arrestor, you can't avoid the first thing you should look at is the cause - worn or broken rings, valve seals or pistons. You need to do a compression check. Avoiding it is putting off knowing what the issue is.

 

[BlueVIP]

I will receive my spark plugs in mail tomorrow and plan to do compression then. When doing that will i need to have the water muffs hooked up so it doesnt hurt the impeller?

 

[achris]

You need to run the engine until it's warm to do the compression test. Compression testing a cold engine will give invalid results. So yes, you need the muffs on.

Chris....

 

[BlueVIP]

Update. Got new plugs in and new fuel filter and cleaned flame arrestor. Compression test all cylinders between 170-175. Hooked it up to muffs still seems to be running a little rich and rough at idle. When I give a little throttle not in gear of course it runs fine. What you all think?

 

[achris]

With the engine running, pull one plug lead at a time to ensure each cylinder is contributing. If all ok, take it out on the lake and run it like you stole it for about 20 minutes... Clean out all the built up crap in the cylinders...

Chris...

 

[BlueVIP]

Not exactly sure what you mean by pull one lead off at a time to make sure each cylinder is contributing? Like may be distributor or plug wire at that point? Sorry not Super mechanical still learning

 

[Yegboats]

Eng: 0f069737 443l1003s mercruiser 4.3lx alpha
drv: 0d888560 50101843s mercruiser alpha 1.84:1
trn: 0f085957 6010000fs mercruiser alpha transom

 

[achris]

Not exactly sure what you mean by pull one lead off at a time to make sure each cylinder is contributing? Like may be distributor or plug wire at that point? Sorry not Super mechanical still learning

While the engine is running, using a set of insulated pliers, pull the lead off spark plug #1. Take note that the engine dropped revs. Push the lead back on and then remove the lead from plug #3, make sure the engine speeds drops by about the same amount. Then put it back on. Do the same with #5, then #2, #4 and #6. Each cylinder, when the lead is removed from its spark plug should cause a loss of revs, usually about 50 to 100. This indicates that all cylinders are contributing to the engine running, and by the same amount. If the engine exhibits no loss of revs when a lead is pulled, that cylinder has a problem that needs to be investigated.

Chris........

 

[BlueVIP]

Ok so after I did the compression check, replaced all plugs and put in water it runs great. By great I mean no stalling no cutting out. It continues to smoke a little. You think I still need to pull each plug wire at a time? Or is this normal?