high engine idle

[bgdg0606]

I figure I start a new thread on this issue. I have a 88 ebbtide with a OMC I/O motor with GM block 4.3 Liter v6. After starting the engine the rpm is at 2800 to 3000. The carburetor is new and adjusted as low as i can get it but the rpms wont come down. Any suggestions.

thanks

 

[Bt Doctur]

Re: high engine idle

And the type of carb is???

 

[JustJason]

Re: high engine idle

3000RPM Idle?

Me thinks you don't know how to adjust a carb, and what all the screws actually do. Heck even an air leak someplace wouldn't get you that high.

88 OMC, 2 BBL Holley carb right?

 

[Jeepster04]

Re: high engine idle

Is the RPM gauge showing 3,000rpm? Does the engine actually seem like its running at 3,000rpm idle? Have you checked that the gauge is correct?

 

[bgdg0606]

Re: high engine idle

rochester carburetor 2 barrel. and its showing 3000 rpm and seems likes its doing every bit of that

 

[Bt Doctur]

Re: high engine idle

You have the idle speed screw all the way out and it still races?
Try unhooking the throttle linkage and let us know.

 

[bgdg0606]

Re: high engine idle

throttle linkage unhooked and screw all the way still races to 3000 rpm. But did notice if i put hand over the top of the carburetor and it sucks my hand hard and if i give it just a little air i can get to run about 800 - 1000 rpm.

 

[JustJason]

Re: high engine idle

Okay, start with the basics. Why did you put a new carb on it, what was wrong with the old one?
What is your base timing set to?
Did you remember to use a base gasket???

 

[Bt Doctur]

Re: high engine idle

New carb out of the box or rebuilt .If rebuilt ,by who?
Almost sounds like the throttle plates are not fully closing at idle.

 

[bgdg0606]

Re: high engine idle

new carburetor put on cause the choke shaft assembly was broke so i picked up a new one. did use a base gasket. and going to have to check the timing.

 

[JustJason]

Re: high engine idle

your not going to be able to check timing unless you do it cranking with the plugs out, the rpms are way to high.
It does sound like the throttle plates are not closing, or one hell of an air leak.
With the throttle cable off have someone start the boat for you, and see if you can push the throttle plates closed with your hand using the linkage on the side.

Also get yourself a can of this stuff..

http://www.theoutboardwizard.com/images/6in1_penetrating_lubricant_evinrude_250x250.jpg

If you don't have a j/rude dealer near you, find a cycle shop, the Bel-ray brand is the same stuff.
Use it and spray the carb base, spray the linkage that enters the carb, spray all around the edges of the intake manifold. If you see the oil get sucked in, you have an obvious air leak. Try choking the motor out by hand like you've been doing. It's easier to find a leak if the RPMS are down some.

Was it orignally a rochester carb on it as well? or did you switch brands.

 

[nailem]

Re: high engine idle

try to loosen the distributor bolt and slightly move the distributor one way then the other with the motor running and see if it brings the rpms down.

 

[Black as]

Re: high engine idle

Do you hear any air leaks or forgotten to fit any hoses to the carby.

 

[Juniinc]

Re: high engine idle

I'm thinking U got a vacuum leak,,,
common leak paths are carb gaskets, carb insulator spacers, intake manifold gasket, maybe a cracked intake.
Aerosol carb cleaner can be used on suspected leak points while the engine is idling.