Carb adjust doesn't smooth idle

[chris in houston]

Bought a 2000 Bass Tracker with same yr 60 HP Tracker Merc (3 cyl, 2 cycle). Motor runs great off idle, but idles a little rough at 700 rpm (on dash tach) in gear. I played with idle screws on carbs, but between too lean and too rich could not find a happy smooth setting.

As I leaned out each carb, RPM did not climb - just started stuttering once I got too lean. Also, blue smoke seems a little thick at idle, like it's maybe too rich.

Also, even when warm I need to push throttle forward in N to get to start without it dying. Then when I back throttle down to idle it will stay running, though a little rough. As throttled up to speed, there is a perceivable RPM at which it goes from what seems like a miss to a smooth, all cylinders firing acceleration.

Plugs have been replaced in last 12 months. Wires look OK. Not sure carbs have ever been worked on.

Fine Merc people, please weigh in on how I can get this thing smoothed out. Thanks!

 

[crem1]

Re: Carb adjust doesn't smooth idle

You have to take the carbs off and let them sit for at least 24 hours in a solvent. Sounds like you have dirty carbs. Make sure you get new replacement parts in a carb kit

 

[ENSIGN]

Re: Carb adjust doesn't smooth idle

Before tearing things apart,CHECK THE GAS,Carbs just don't go bad for no reason at all.

 

[chris in houston]

Re: Carb adjust doesn't smooth idle

What am I checking gas for - water in tank? Is there some additive I can put in that will cure water prob?

Also, is there a carb cleaner gas additive that will really make a difference? If so, I'll try that before touching carbs. Carbs scare me!

 

[ENSIGN]

Re: Carb adjust doesn't smooth idle

Yes you are checking for water.Pump some gas into a clear container and let it settle.If it seperates you'll be able to see the water at the bottom.Don't waste your money on fuel additives,pump the tank out and install a fuel/water separator

 

[crem1]

Re: Carb adjust doesn't smooth idle

"Before tearing things apart,CHECK THE GAS,Carbs just don't go bad for no reason at all".
Carbs do buid up gum deposits which impede normal functioning of the carbs. Carb cleaning is a must

 

[chris in houston]

Re: Carb adjust doesn't smooth idle

Never seen Merc carbs: what parts need replaced and what adjustments need made as part of carb cleaning?

Floats need adjusted?

Also, is there an accelerator pump that needs replaced in these carbs?

I'm hoping just gaskets are replaced and only the idle mix needs adjusted. I could probably handle that.

 

[crem1]

Re: Carb adjust doesn't smooth idle

To start, getting a manual for your model would be helpful. To do a half decent job you have to unscrew the carburator from the powerhead, then remove the old filter from the bowl, take the idle mixture screw out and put all of them in a carb cleaning solvent. Let it soak. Go to a MERC dealer and ask for a carb replacement kit.

 

[Faztbullet]

Re: Carb adjust doesn't smooth idle

That motor doesnt idle really smooth dure to the 3 cylinder design,and you must have it in a can or lake with backpressure to adust carbs due the exhaust scavaging on that model. Try that first before you tear into anything..also the check valves behind the reed plates can stick causing a rich idle as fuel puddles in intake manifold.

 

[chris in houston]

Re: Carb adjust doesn't smooth idle

Faztbullet, the "check valves behind the reed plates"; are those the check valves in the tubing that connects behind the carbs? I read elsewhere to use a syringe to check them for leaking. Should they flow from the top carb to the middle carb, and from the mid carb to the bottom carb? Are these cheap little parts I can get at any Merc parts shop?

 

[crem1]

Re: Carb adjust doesn't smooth idle

In order to check the reed valves properly, one must remove the carbs from the powerhead

 

[Faztbullet]

Re: Carb adjust doesn't smooth idle

Click on link below and they are #8 in diagram. Before you do this this is what I would check..
1) Compression is equal on all cylinders
2) Primary and pick-up timing is correct
3) Carbs are sync'd
4) Carb settings are at factory spec's
5) Pull front air cover and check each carb to see if it maybe slightly flooding at idle
6) Fuel is fresh
7) Engine is decarboned

http://www.mercruiserparts.com/Show...0&bnbr=140&bdesc=CYLINDER+BLOCK+AND+CRANKCASE