1991 OMC 4.3L Will not idle under 1400 RPM

[kylep123]

Hello,

I have a 1991 OMC with the 4.3L GM engine and a 4160 Holley carburetor on it. The original owner had a brand new motor put into it as the person who winterizes it for him forgot to winterize so his insurance covered a new engine. Since i purchased the boat i did notice the idle was a little rough and high so i decided to tear into it and get it running right. It runs rough, almost rocking the whole boat, not like i have seen online and the idle is at 1400 RPM if i try to adjust it down it will just die. I did rebuild the carburetor and cleaned it all out and still the same thing. I have changed the coil pack, wire and plugs still nothing. Last night i went to start it and the secondaries were just pouring fuel so i will take it off and maybe something got lodged into the needle but i am still at a loss of why this engine is running so rough and will not come down in idle. Is there anything i am missing or a simple trick to get this right i do not want to ruin the unit when shifting into gear at such a high RPM. Thank you in advance.

 

[Scott Danforth]

first, disconnect the throttle cable to rule that out for holding the idle up. if it still will only idle at 1400, then dies if you try to back off the throttle plates, actually pull the carb apart, soak it for a day or two and chase out the idle passages with a fine piece of copper wire or fishing line. it sounds like your idle circuits are plugged.

did you also change the power valve when you had the carb apart? if so, what number did you replace it with?

 

[Earp]

You tried a compression test?. A motor with a few bad cylinders will still run at 1400 rpm. There are lots of sketchy engine builders out there.