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Thread: Had to prime it today

  1. #1

    Had to prime it today

    Went to take the boat out for a ride last night and it cranked like crazy but would not fire. It's my 251 Catalina with a 350 mercruiser. So now I open the engine hatch, take off the spark arrestor and don't see any sign of gas in the carb. I went and got a little gas and dumped a tablespoon down the primaries and it fired right up. After warming up it ran perfectly. Out in river it was strong as ever. This morning I went down to the boat to check it out and same thing. It wouldn't start till I primed the carb and then was ok. Does it sound like the fuel pump is on it's way out? Why does it run strong once started if the pump is going. Thanks-Russ

  2. #2
    If it's still got the original Rochester Quadrajet carburetor on it, it sounds like the main well plugs have started leaking.. It's a common problem with those carburetors.. When the well plugs start leaking, it drains the float bowl down into the intake manifold, when you go to start it back up after sitting overnite, you have to crank the engine for an extended amount of time to refill the carburetor float bowl..

    There's all sorts of homegrown "fixes" for this problem, but the permanent "fix" is to replace that "Quadrajunk" with an Edelbrock Marine Performer 600CFM carburetor..
    CC-John

    1978 251 Catalina Express
    Powered by: PCM 383 CID GM (Bored & Stroked Chevy 350, 330 HP)

    1973 Century Resorter 16
    Powered by: 1972 Chrysler LM318 (225 HP)

  3. #3
    I've cranked it 10 seconds at a time, 3 or 4 times and it still won't pump fuel up to the carb? I already ordered a reman quadrajet for my 5.7 mercruiser 260. I know what you mean by the plugs leaking. The reman carbs have them epoxied to eliminate that.

  4. #4
    Well maybe I didn't tell you the whole story My friend said that I should have a pcv system on the motor. I went and bought 2 pcv valves and a T fitting to plumb into the rear of the intake manifold. THAT'S WHEN IT ALL BEGAN I couldn't start it until I primed the carb. My one Son that is a tech at a GM dealer said that it won't start because with that big line plumbed into the intake, for the 2 pcv lines going to the valve covers it's like a big vacuum leak and something about crankcase pressure causing the carb not to suck fuel into it.

    Well to make a long story short I put the pipe plug back into the intake and directed the hoses from the valve covers to the spark arrester again like it was and it starts every time now

  5. #5
    No one made a PCV engine for a boat until Mercruiser did it in 1992. By 1993 the EPA was coming down hard on boat and engine manufacturers. The two hoses that connect to the 90-degree barbs on the valve cover do run to the flame arrestor to recirculate the natural occurrence of blow-by from the engine, it is an open system. It does not plug into the manifold, in the only the tops of the valve cover and flame arrestor. The worst advice in the world usually comes from a friend who knows nothing but is describing how to do it....
    WP_20151107_16_04_01_Pro.jpg

  6. #6
    Well today it wouldn't start again. Carb is dry, telling me what CC-John has said. The carb must be leaking down and there is no gas in it for the accelerator pump to shoot fuel in to start. Looks like a good idea I ordered that new carburetor

  7. #7
    I had the same thing going on, I changed out the fuel pump. Cheap, got it from summit racing. Problem never came back. My carb had a recent rebuild so I looked toward the 30 plus year old pump. Worked for me, good luck!
    1982 Catalina 251 "OLD SCHOOL"

  8. #8
    One of the men at the marina says it may be the anti-siphon valve in the fuel line at the tank.

  9. #9
    Footbrake, that is exactly what is going on. To verify it, lift the carb up you will be able to see the gasoline streaks in the intake manifold without looking at the carb, then once you drain the carb flip it over and you will see the places that it is leaking, right under you primary and secondary needles from the well plugs.
    Q_jet_well_plugs.jpg
    The best, fast and easy repair is to completely drain the carb, apply JB-weld over the well plugs let it dry for 24 hours, reinstall reset/check the float level and you're done with it. As CC-John said, Edelbrock and Carter carbs are far less troublesome than the Q-junk.

    As a side note, if you are buying from National Carburetor, http://www.nationalcarburetors.com/m...rochester.aspx make sure it has the correct marine bowl vent 4.jpg and that it has an ethanol friendly Accelerator Pump, if not the old cloth Accelerator Pump will break down and give you all kinds of headaches.

    My prefered carb go to guy is Mike at Mike's Carbureators, he knows his stuff fast turn around times and can find all those hard to find carb parts http://www.carburetor-parts.com/Marine_c_29.html

  10. #10
    Try taking the fuel line off at the carb. Stick it in something and carefully crank the engine. Good check to see if it's the pump or anti siphon valve. If the carb is getting gas it has to be the carb.

    Eliminate 1 thing at a time.

    Another reason I went EFI. If the carb works, no problem, but when it doesn't.....
    1983 280 Catalina

    "When in danger, or in doubt.
    Run in circles, scream and shout."

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