Mercruiser 5.0L carburetor issue??

[backyardmechanic]

1994 5.0 mercruiser, i did a complete tune up this spring, coil, take up coil, distributor cap and rotor, plugs, completed timing as well. it has been running fine then last week it started to stall during low idle 1000-1500 rpm. I have to go to 2000 rpm to keep it going otherwise it stalls. i have put stabilizers in the fuel. i don't think anything has been done to the carburetor but i'm just wondering where you would begin with this kind of problem.

 

[mthieme]

Re: Mercruiser 5.0L carburetor issue??

Have you tried adjusting the mixture screws?
Or looking down the carb to see if it's dumping (dripping) fuel?

 

[dan t.]

Re: Mercruiser 5.0L carburetor issue??

take out tht idle mixture screws, blow thru the holes with compressed airwhile opening and closing the throttle,replace the mixture screws, turn all the way in,back them out 3 turns,start the motor ,set the screws equally to the best idle. most of the time this will cure ano idle situation,good luck

 

[achris]

Re: Mercruiser 5.0L carburetor issue??

take out the idle mixture screws, blow thru the holes with compressed air while opening and closing the throttle,replace the mixture screws, turn all the way in,back them out 3 turns,start the motor ,set the screws equally to the best idle. most of the time this will cure an idle situation,good luck

Which means there is crud in the carb... Time for all filters to be replaced and maybe consider stripping and cleaning the carb... 14 years? .. Yep, it's time....

Chris.......

 

[mthieme]

Re: Mercruiser 5.0L carburetor issue??

Yep, probably the case. It sounds like he hasn't touched the carb at all.

I highly recommend not blowing compressed air into any carb orifices unless your taking it down. I've seen the seat/needle damaged from this and also floats stick.

 

[dan t.]

Re: Mercruiser 5.0L carburetor issue??

I agree ,the carb probably does need an overhaul,I suggested this as a quick fix. if you know anything about carbs ,you would know that the idle curcuit has nothing to do with the needle valve or float. this is a common every day fix in the automotive trade, or at least it was when carbs were common

 

[mdillon411]

Re: Mercruiser 5.0L carburetor issue??

The carb on my 5.0 was rebuilt about 2 months ago. We took it on a watersking trip and it worked superbly. Then coming in one day it stalled as I was docking the boat. It hasn't been right since. Key off - no electric at the exc terminal . Key on - electric is at the exc terminal.
I just read this:

take out tht idle mixture screws, blow thru the holes with compressed airwhile opening and closing the throttle,replace the mixture screws, turn all the way in,back them out 3 turns,start the motor ,set the screws equally to the best idle. most of the time this will cure ano idle situation,good luck

I don't think this applies to me because of the recent rebuild.

Any other ideas?

Thanks,

MADillon

 

[zbnutcase]

Re: Mercruiser 5.0L carburetor issue??

MADillon, welcome! However you should have started your own thread. That said, It wouldn't hurt to remove the screws and blow out the passages; I have seen rebuilt carbs contaminated instantly by dirty fuel, flame arrestors, etc. Because it was rebuilt 2 months ago doesn't mean it can't have probs now. 'nutcase

 

[intrepidvoyager]

Re: Mercruiser 5.0L carburetor issue??

think you will find pressurized carb cleaner with the little red tube is better than compressed air !

Why .... well ...

compressed air via compressor may not be readily available.

cans of compressed air like used to clean a PC are difficult to work with, freeze up, etc.

compressed air does not clean off fuel glaze.

if you are trying to see if an idle circuit is ok ....... with compressed air you cannot see the air coming out of the venturi port .... with carb cleaner you can see the cleaner squirt out.

Depends on the type of carb but usually if you open up the throttle plate and shine a light in the carb venturi and pull an idle screw and stick the red tube in the idle screw port and give it a 3 second blast of cleaner you should see fuel coming out of the venturi idle port. If not do it the other way round.

Carb cleaner is also a good solvent for other uses, however be aware that some brands contain toluene and xylene.. ...