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Vapor lock

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  • Vapor lock

    Periodically I would have a problem with the fuel system vapor locking on my engine. Ever since I installed a half freshwater system on the engine it has gotten a lot worse. The mechanical pump on the engine is new. I didn't want to but I did purchase a marine electric fuel pump. Is there a better way to help prevent this other than installing an electric pump? If I install the electric pump can I use it only when the engine vapor locks? If so can I plumb the electric pump in-line after the filter and pump it to the manual pump? In other words can I supply the mechanical pump with the electric pump and will the mechanical pump draw through the electric pump if the electric pump is not being powered?
    1980 pilot house 351
    1988 260 predator 351

  • #2
    Where is the problem occurring. Usually between the fuel pump and the carb where the fuel line runs close to the block. Hot spot.
    1988 26' cuddy
    1975 20' open
    31 Grand Slam
    16' Sandpiper
    14' Certified Fiberglass

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    • #3
      Very often vapor lock is blamed but not the issue. As Jerry said if you did have vapor lock it usally only happens with the steel line to the carb that would get hot enough to turn the gas to vapor. If the engine is running at 180 degrees it is rare to have this happen. The more likely case is a carburator draining when shut off and then no fuel to restart and to warm for the electric choke to operate. Just some thoughts from 500 miles away.

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      • #4
        I agree with both Jerry and Reelhappy. I would 1st try to insulate the line from the fuel pump to the carb and see if you problem goes away. If your problem goes away it was vapor lock, if not you have the problem that Reelhappy was speaking of. I had a problem with the carb draining back once but it never gave me a problem once the engine warmed up. Mine didn't want to start when the boat sat for a week or so. I changed the fuel pump and the problem went away.
        Clyde, Pasadena, Maryland
        1985 Shamrock (ROCK SOLID)26 Cuddy Cabin
        2000 Yanmar 4LHDA-STE 230 HP....
        Hurth HSW 630 A1 1.6 1.58 Trolling Valve
        17X17 4 bladed Prop with Light Cup

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        • #5
          2 of my boats have a problem of the fuel draining. I close the valve when done for he day.
          1988 26' cuddy
          1975 20' open
          31 Grand Slam
          16' Sandpiper
          14' Certified Fiberglass

          Comment


          • #6
            This happens only when I run the boat for a good period of time and then cut it off and maybe go into a restaurant or something and eat lunch. When I come back and starts and idles for a few minutes and shuts off and won't restart. I've taken the fuel line off the carburetor and ran it into a bottle. Turn the engine over and it barely barely pumps any fuel. A raise the engine hood and let it cool for about an hour and it fires right up and stays running. The fuel filter is new. The vents are clear. It seems like it's worse since I put that half system on the engine. I'm thinking maybe it doesn't dissipate the heat is fast.
            1980 pilot house 351
            1988 260 predator 351

            Comment


            • #7
              I'm wondering if it's the pump. Is it a Carter? There was a batch of bad ones not so long ago. Naturally all made overseas now.....

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              • #8
                When you remove the fuel line if it was vapor locked that would remove the vapor lock. Any chance you have a spare fuel pump laying around that you could try, maybe on your other boat??? I'm thinking maybe the check valve in the pump is defective.
                Clyde, Pasadena, Maryland
                1985 Shamrock (ROCK SOLID)26 Cuddy Cabin
                2000 Yanmar 4LHDA-STE 230 HP....
                Hurth HSW 630 A1 1.6 1.58 Trolling Valve
                17X17 4 bladed Prop with Light Cup

                Comment


                • cw.abeljr
                  cw.abeljr commented
                  Editing a comment
                  Another thought is possibly you have a bad connection or pin hole in your fuel line somewhere and the added pressure buildup from the heat when running is bleeding off when it sits cooling. But I would think if that were the case it would loose power when WOT.
                  Last edited by cw.abeljr; 07-13-2019, 03:29 PM.

              • #9
                Originally posted by My My Hey Hey View Post
                ........ I've taken the fuel line off the carburetor and ran it into a bottle. Turn the engine over and it barely barely pumps any fuel. ..........
                Is the suction line (from valves/filters to the pump) clear of a heat source, such as the exhaust manifolds?

                C Rhodes
                26' Mackinaw - 1990
                351 Indmar (1990-2006: Great Engine)
                351 PCM (2006 - Current)
                Southport, NC

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                • #10
                  Thanks guys. It's got to be the pump. It messed up all day today. This time it happened as soon as I cut it off and try to restart. It would run the gas out po f the carburetor and shut off. The pump would barely pump fuel. I could disconnect the suction hose from the pump and draw it easily. I hate the taste of gas. Does anyone have a good source for a good quality pump? Thanks
                  1980 pilot house 351
                  1988 260 predator 351

                  Comment

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