3.0 mercrusier runs badly after it warms

[Anthony Nardella]

Mercrusier 3.0 Motor starts and runs until it warms up. Then it starts to run rough and eventually stalls out. The engine recently had a tune up. Cap, rotor, wires and plugs. New fuel filter and pump seams to be working. I tested the enrichment valve circuit and hot wired the valve. Circuit and valve both working. We also took the carburetor off and checked the inside for dirt. Looked really clean. The main jets working well. The only thing I noticed that looked funky was when I took off the coil wire and cranked the engine sparks were flying out of the coil area. Not sure if that’s normal???

 

[Bondo]

We also took the carburetor off and checked the inside for dirt. Looked really clean.

Ayuh,..... "Looking" into the carb is a long, Long ways from rebuilding the carb,......
It sounds like you got a lean condition goin' on, so a carb "Rebuild" is where I'd start,.....

 

[Scott06]

The only thing I noticed that looked funky was when I took off the coil wire and cranked the engine sparks were flying out of the coil area. Not sure if that’s normal???

If you take the coil wire off and dont ground it the energy for the spark needs to go somewhere so it will arc off the coil to where ever it can find a ground. All this say to me is you have a good spark coming off coil

As bondo said did you strip and clean the carb internally ? Have you tried to set idle speed and mixture

 

[Anthony Nardella]

If you take the coil wire off and dont ground it the energy for the spark needs to go somewhere so it will arc off the coil to where ever it can find a ground. All this say to me is you have a good spark coming off coil

As bondo said did you strip and clean the carb internally ? Have you tried to set idle speed and mixture

Yes I cleaned the and sprayed carb cleaner through everything. Didn’t have the tool to adjust. I’ll try that next.
Thanks

 

[Scott Danforth]

Yes I cleaned the and sprayed carb cleaner through everything. Didn’t have the tool to adjust. I’ll try that next.
Thanks

You did nothing.....

To clean a carb, you must remove the carb, disassemble the carb, siak the carb in carb cleaner, mechanically scrape gaskets, mechanically probe circuits, flush debris out, reassemble the carb and then set/adjust as needed.

Spraying carb cleaner at most cleans the exterior of the carb that is not affected by dirt.

You could have 30 pounds of mud surrounding the carb and not affect how it runs

However, just a few grains of debris or corrosion inside the bowl and circuits and you get a motor that doesnt run

 

[alldodge]

What carb is it, a TKS or Merc?
Got a serial number?

 

[Anthony Nardella]

You did nothing.....

To clean a carb, you must remove the carb, disassemble the carb, siak the carb in carb cleaner, mechanically scrape gaskets, mechanically probe circuits, flush debris out, reassemble the carb and then set/adjust as needed.

Spraying carb cleaner at most cleans the exterior of the carb that is not affected by dirt.

You could have 30 pounds of mud surrounding the carb and not affect how it runs

However, just a few grains of debris or corrosion inside the bowl and circuits and you get a motor that doesnt run

Thanks for the recommendations. I threw the towel in on this repair. I hired a pro he came in rebuilt the carburetor “totally” and hooked up a small gas tank. The motor ran perfectly on high and low idle. He also ordered me to drain the tank and refill with fresh fuel. I’m left thinking sometimes it’s not the parts but the liquid. All good thanks for your help everyone.
Anthony Nardella

 

[Bondo]

Thanks for the recommendations. I threw the towel in on this repair. I hired a pro he came in rebuilt the carburetor “totally” and hooked up a small gas tank. The motor ran perfectly on high and low idle. He also ordered me to drain the tank and refill with fresh fuel. I’m left thinking sometimes it’s not the parts but the liquid. All good thanks for your help everyone.
Anthony Nardella

Ayuh,...... Now would be the perfect time to plumb in a Merc water sep. fuel filter, just before the fuel pump,......
That'll catch any crud before it becomes a problem, 'n is a great diagnostic tool when the motor don't run right,.....
The contents of that filter can contain clues as to why it quit runnin' right,....

 

[Anthony Nardella]

Ayuh,...... Now would be the perfect time to plumb in a Merc water sep. fuel filter, just before the fuel pump,......
That'll catch any crud before it becomes a problem, 'n is a great diagnostic tool when the motor don't run right,.....
The contents of that filter can contain clues as to why it quit runnin' right,....

We’re on the same page! I went in hard. I install the correct racor fuel water separator filter. Changes all the lines as well. Clean as a bell! Learned a good lesson!!!
Thanks again.
Anthony Nardella