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Mercruiser 305 - Quadrajet Rich Idle

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ddkjunior:
Thanks for the advice - it appears to be more than nozzle drip.  I adjusted the idle speed screw so the primaries would close and the mixture screws were still ineffective from fully closed to 3.5 turns out.  I advanced the timing a while back so I could get decent vacuum...about 15 inches was the most I could get...so I think the timing should be good and it runs awesome above idle.

At idle its loading up and flooding quite a bit and when it stalled out I could see fuel seeping out of the base and a little out of the accelerator pump.  Not good on a boat.  Looks like I'll have to pull it and check the float, needle and seat.  Could be getting too much fuel pressure as well but I don't have an easy way to check it.  It has a brand new (not rebuilt) Mercruiser fuel pump and I'm hoping I don't need a regulator or need to try another fuel pump.

Thanks again.

Shark Racer:
Did you look down the airhorn and verify the boosters were not dripping?

What kind of fuel pump is it? Electrical or mechanical?

von:
Some aftermarket replacement fuel pumps have to much pressure for a Q jet to handle. Ones I  had were around 9 psi. I've had two of them and finally got an AC Delco pump that was OK at 5 psi. A Q jet usually can only handle about 6 psi depending on needle seat size. The bigger the less pressure they can withstand. That said, if you have a leak between the needle seat and main body, that will cause flooding. BTDT. Sometimes the body seat gasket sealing surface gets eroded or boogered up or sometimes the old gasket doesn't get removed and stays in place then a new gets placed on top of it. Of course a defective float or needle and seat or wrong float setting could cause it too. One other thing; many times people incorrectly install the tiny clip on the needle through a hole in the float arm. That could possible cause a problem with the needle getting hung up and not seating completely. It should hang from the outer edge of the float arm (hard to explain without a pic). Many people including me leave the clip off entirely.

ddkjunior:
This was a brand new Quadrajet but I knew it probably sat for quite some time.  I tried to leave it alone as much as possible but had replaced the Nitrophyl float with a brass one along with the accelerator pump.  I put the original float back in it and adjusted the level from the recommended 9/32" to about 11/32" just to be safe.  It does not flood now and runs great!  It idles fine but the mixture screws are still pretty ineffective.  I'm guessing it's still a bit on the rich side but starts and runs excellent so I'm going to leave it alone for now.  Thanks for the help.

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