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5L Mercruiser 2bbl wonbt idle

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ray_ralph

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"I can't keep my 5L Mercru

"I can't keep my 5L Mercruiser running at idle. Engine is 2004 purchased as leftover in 2005 and installed in Sept.05. Ran great through breakin and last season. Brought from ramp to dock at my home early this summer where it sat. Suspect fuel went bad during winter layover (some of it has been in the tank for a few years) and lack of use during season. Changed water separator fuel filter and cleaned out carb inlet filter. Disconnected fuel tank and running on portable tank with fresh gas. Engine fires right up and runs great but stalls when choke kicks off. Starts right up and runs at about 1500 rpm but will stall when I try to bring to idle. Can't shift into gear. Just want to get boat to ramp to haul. Carb is 2bbl has SAE J1223 MARINE written on it. Single Idle mixture screw but it has a seal on it.
Tried carb cleaners, Seafoam and WD40 all improved things a little but still stalls. Also even replaced distributor cap and rotor since it seemed to have some moisture.

Any suggestions to get it running enough for the 15 minute trip to the ramp?"
 
"Carb idle circuits plugged w/

"Carb idle circuits plugged w/varnish. If Bt. Dr.'s suggestion doesn't help, rebuild carb and pump out old fuel from tank.

Try this cheap fix first. Empty the fuel/water filter and fill w/Sea Foam. Run engine for 5-7 mins. and shut off; let it soak overnight and restart."
 
"Thanks for the quick response

"Thanks for the quick responses and suggestions.
The "seal" on the idle screw is some kind of cap that I can't easily get off. I can pull it out but it springs back. Tried to turn it off,pull it off, pry it off....it ain't comin'!
Filled the filter with Sea Foam as Guy suggested and ran for 5 minutes. Backfired through carb and sputtered for a few seconds but then ran at about 1200 rpm rest of time. I'll let it sit and see what happens.
Thanks again. I really appreciate both of your suggestions."
 
"I will agree that it is the i

"I will agree that it is the idle fuel passges in the carb. Remove the carb, diassemble the float bowl and clean inside. Pay attention to the passages, they are bronze little plugs with a tiny orifice. Remove the idle mixture screw and pressure air thru it. Before removing it, count how many turns it takes to screw it in till it seats, this way you can reset it after cleaning.

Use compressed air into the idle screw hole and fuel orifices and passages. Carefull not to blow parts accross the room. Use maybe 30-50psi.

Assemble and test.

Also, a tune up is probably in order. Plugs ditributor cap and rotor.

Good luck"
 
PS once you fix it post result

PS once you fix it post results and what solved the condition so we have a record to help others.
 
"Had a simular problem on a 2

"Had a simular problem on a 2 BBL 5.7 two years ago after cleaning the carb from a "would not run for more than 10 seconds" situation.
What it turned out to be was the "electric choke". On the 5.7 (and probably the 5.0) its not really a choke in the sense of a pivoting plate in the bore, but rather it's an "enrichment circuit". There is a pipe shaped thingy on the back of the carb on starboard side of the engine. This is held in with a retaining ring and a couple of small screws. There is an electrical connector on it. I found that I had to remove the whole thing in order to be able to clean out the crap in the enrichment circuit (a couple of passages in the carb body itself). Be careful, there is a spring and plunger and a piston. It's cleanable on the engine, but be careful you don't loose any small parts. A can of "canned air", available at Staples or Radio Shack works well."
 
Here is the update.
Guy Gaspa

Here is the update.
Guy Gaspar's "cheap fix" using Sea Foam in the fuel/water separator filter worked. It took a few days but it seemed to clear things up and I was able to get the boat to the ramp with no trouble.
Did a little research and because the motor has an Ultra Low Emission Rating they cap the idle adjustment screw on the carb base. Still not sure how to get it off but thankfully did't have to go that route this time.
My carb has an electric choke with the pivoting plate. The "enrichment circuit is on the next model year(I think).
Some additional information I didn't include in the original post so as not to confuse the issue. My boat has twin engines. Both crapped out at the same time with the same problem thats what led me to look at the fuel. Unfortunately I cooked the starter on my starboard engine trying to get it running. I already took it out(not a fun job) and will replace it Monday.
Hopefully I can get it running and clear it like the port engine...if not I will rebuild.
At least the boat is out of the water before the bad weather hits......now if only I could figure what to do with 120 gallons of bad gas!
Thanks to everyone for your advise. I really appreciate it. This is a great boaters forum
 
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