Mercruiser 260 won't idle when hot

thsorens

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May 2, 2006
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now to figure out whether to buy a new pump $196 locally or just plumb in a regulator.
 

alldodge

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now to figure out whether to buy a new pump $196 locally or just plumb in a regulator.

Is the pump electric or mechanical? If its electric, what brand/model? I would suggest getting a gauge that reads higher.
 

thsorens

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May 2, 2006
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Is the pump electric or mechanical? If its electric, what brand/model? I would suggest getting a gauge that reads higher.

Its mechanical. I plumbed in a regulator and got it down to 4.5 psi. Doesn't load up now but still doesn't run perfect. Takes forever to warm up before it will idle on it's own but once it does it runs pretty good. I can start it in idle (once warm) and let it idle indefinitely now. Much better.
 

alldodge

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Might need to clean the plugs again from the flooding, but I'm thinking choke issue. Starts and runs fine when warm but has trouble when cold.

If you start having problems at higher rpms later might need to pump the pressure up to around 6 psi
 

NHGuy

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May 21, 2009
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I'd start finding a replacement pump too. That 9.5# stuff is probably a sign of a short future.
Then start rechecking your setup. idle mix, idle speed, timing, jetting, rods & springs, might even need to change the pump shot. Suspect & check your entire carb setup because you don't know how much of it was being influenced by the extra fuel. Or for how long. It's a PITA, but it's also real nice to have it working correctly.
ps. I have always heard to set Quadrajet secondary air door springs to 3/4 turn from contact. But recently saw a post from someone knowledgeable saying to check between 3/8 & 3/4 turn. So if you get any mid speed bog check that.
 

AndreyCat

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Jul 8, 2016
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Taking the chance here in this forum to see if I can get some help! I don't know if this is allowed or not, I have a 4.3 mercruiser that runs good for 20 minutes then it will act like running out of fuel, carb has been cleaned and anti syphon valve replaced with straight fitting, any ideas?
 
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