View Full Version : OMC 57 1981 when warm runs not on all cylinders

Manuel Hurt
04-18-2004, 01:08 AM
" (Sorry for my english)
The engine starts and runs perfectly for the first 15-30 minutes. Then when I switch it off and restart, the engine runs not on all cylinders. I can't say which cylinders.
The engine has 550 hours, plugs, wires, oil, oil filter are new. The distributors cap is clean and works well.
If it is not an electric problem, could it be from the carb ? Or could it be stucked valves ? The auto choke works well, the flap is fully open while engine is warm.
Could it be the compression ? But the oil is clean. So many questions.. thank you in advance for your help.

PS: While engin runs not properly, when I put rear gear, the engine coughs and stalls. "

04-18-2004, 09:13 AM
" Manuel,
Heat activated igniton problems are characteristic of a bad coil, however it could be a bad condenser ( if you have points ) . Replace the condenser first as it is not expensive. If that dosen't do it, put in a new coil
Eddie "

04-19-2004, 08:33 PM
"I agree with Eddie that ignition is the place to start. One other possibilty is mild vapor lock in the carb from engine heat. You didn't say if the engine would keep running normally beyond 30 minutes or if the miss goes away a short time after restarting.


04-29-2004, 07:49 AM
" Thank you for your help. I now changed the condenser, the coil and points, but I am still not happy with the engine. Cold or warm, sometimes it runs perfectly and sometimes less.
And when it is very warm, I just can't accelerate, or only very slowly.

I put gasoline additive in the tank in case of condense water. Do I need to change the gas filter ? Or cleaning the carb ? If yes, can I do it myself ?

Thank you in advance "

04-29-2004, 07:29 PM
" Manuel,
Pull each spark plug one at a time. They should all look good when new or have a light grey ash. Ones that are black indicate misfiring. In that case you might have a defective new plug wire or got a hair line crack in the porciline part of that spark plug.
Eddie "

05-04-2004, 01:03 AM
" The plugs are dry and have a light grey ash. When I start the cold engine, black smoke comes out the exhaust and it dies on idle. After two minutes it runs fine with any rpm. But when engine is hot, after having cruised for minutes with 3-4000 rpm, the engine dies on idle. For restart, I must give full throttle. It starts, but very much black smoke comes out the exhaust. After 2 minutes running a bit higher than idle, it runs fine again on idle.
Do I need to clean the carb, and if yes, how ? "

05-04-2004, 04:57 PM
" Manuel,
Sounds like the choke is staying shut until the choke pulloffs override and open the choke plate.
Eddie "