Mercruiser Quadrajet

[pinbodean]

Hi all,
I have a 1996 Regal 8.3 Ventura with a Merc 7.4 Bravo 3. Last fall it became super hard to start if it sat for a few days. It turns over just fine. Pump the throttle 1-20 times, doesn't matter, won't fire. The choke is fully closed. If I pour a little gas down the carb, it fires up and runs great. I thought it might be the accelerator pump,(didn't have a chance to look down the carb) but the boat runs fine; no bog or hesitation. I know auto carbs have 2 soft plugs on the bottom of the carb that tend to leak and empty the float bowl after a period of sitting; do marine carbs have these plugs? I've rebuilt a couple of Holleys but I've never rebuilt a Q-jet before....kinda leery about it. Any ideas or words of encouragement would be greatly welcomed.d

Pinbodean

 

[Reel Poor]

Re: Mercruiser Quadrajet

Hi all,
do marine carbs have these plugs?

Pinbodean

Yes they do, and they have been known to be a problem.

 

[Silvertip]

Re: Mercruiser Quadrajet

Q-jets have also been known to have porous castings which also allows them to leak down and cause hard starts when cold due to lack of fuel in the float bowl, and hard starts hot because of the fuel being dumped into a warm engine. Most kits had a rubber pad that sealed off the leaky plugs. Some rebuilders were using an epoxy-like coating to seal up the float chamber but I've been away from the carb scene for so many years I don't know how that stood the test of time. As for rebuilding, the carb is not difficult to work on but adjustments must be spot on for proper performance. The air valve secondary spring has a tendency to let go, get weak, or out of adjustment which creates a terrible bog as you hammer the throttle.

 

[Brendija]

Re: Mercruiser Quadrajet

Yeap! That carburator has the plugs. If you are ready to work on it. Clean first the part where those plugs are and with epoxy seal the hold and make it flat even with the bottom part of the carburator. Always use a marine rebuiding kit for it. It's easy to work with it and make shure to put averything back like it was before. Do not overtite the 4 intake bolts mounting the carb back on the engine. Do it evenlly, that will not bent the carburator itself. Good luck.