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1979 260 mercruiser idle

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King48

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I have a 79 mercruiser mcm 260 that will idle for 5-10mins and the it will start to surge and lose rpms till it dies I can stop it by adding throttle it also idles at 1 to 1.1k rpms and can't get it any lower. I've rebuilt the carb but didn't change at all any help will be great. No idea if it matters but the drain petcocks in my exhaust risers are gone trying to find something to screw in to them to stop my bilge from filling up
 
Re: 79 mercruiser idle

Welcome aboard !

You could tap it out and try a one size bigger brass pipe and a cap, then when you want to drain it just remove the cap, and always poke the hole with a wire bent tip to remove the rust so it doesn't block the hole. Any plumbing supply with have it.

How does the dist look, the shaft loose, the rotor loose what?

The filters clean, the one at the fitting that enters the carb, the sep, if you have one the fuel pickup tube and anti-syphin valve.

Have water in the tank?

First check the dist and run it on a external tank of gas, clean fuel. Still doing rebuild the carb again and do it right. Want help just ask. I'll look for a old post i made about carb rebuild.
 
Re: 79 mercruiser idle

How is the fuel pump? Is there fuel entering the carb via the plastic hose from the fuel pump? Did you check the timing? Does the engine respond to the idle/mixture adjustment screws? Did you adjust the idle speed screw to bring down the RPMs?
 
Re: 79 mercruiser idle

Ya fuel is good I know since i pulled the gas tank and cleaned it out still had what looked to be either really old gas ur leaded gas haven't checked the Ignition system yet but I'll give that a look but it all looks new from a glance but the coil and yes I've tried to lower the idle with the screw but will die as I try to lower the rpm
 
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