Question Portable Gas Tank Question

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  1. #1
    Dedicated TF Poster - Not a Tidal Fish Subscriber
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    Default Portable Gas Tank Question

    My first 3 boats all had built in fuel tanks. My current 17' jon boat (25HP 4 stroke Merc) has a Portable 7 gallon gas container. I try and remember to fill it after each and every trip. Last several trip when I unhook the plug from the motor, I lose vacuum and have to pump primer bulb several times to make it firm again. On my most recent trip I could not get my primer bulb to get firm. I was getting frantic and other boats were waiting to launch so I tried to start the motor and it fired right up? Strange...in my previous boats if primer bulb was not firm, I could not get my engine to start.

    So why is my primer bulb not getting firm? Is just the primer bulb bad or the entire line from portable tank to motor? I looked at hose and I see no visible evidence of air getting into the system to lose pressure/vacuum.

    Second question...Why did my motor start even without primer bulb being firm. I tried this 3 times (including last night) and the motor fires right up on 1st or 2nd pull. I know on my past boats this would've been a deal breaker not having a firm primer bulb.

    Any suggestions on what I should do is appreciated. Trying to stave off the dreaded stuck at boat ramp and motor won't start scenario...

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  3. #2
    Tidal Fish Commerical Lite Subscriber - My business supports Tidal Fish
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    More likely than not the residual gas in the motor's fuel system is what's allowing the motor to start without the primer bulb becoming squeezed hard. My bet is that the motor will start even if you did not attach the fuel hose to it. Try that to satisfy curiosity. Also, try starting the motor after connecting the fuel line to it WITHOUT squeezing the bulb.

    I have found that it is best to position the fuel bulb in a vertical position when priming the motor with the end of the bulb that is closest to the motor at the top of its vertical positioning. That has always resolved the problem (for me) when a bulb refused to get hard.

    I really do not think you have a problem with your fuel system, however, I'm not there to inspect it.

  4. #3
    Average TF Poster - Not a Tidal Fish Subscriber
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    On my merc 25hp 2 stroke I has a clear fuel filter before the carb. I can squeeze the primer bulb see it’s working. And sometimes is doesn't get hard.

    Does your engine have a Carburetor? If so, more than likely the bowl still has gas and the fuel pump is drawing from there. Which in turn will allow you to start your engine without connecting the fuel tank line.

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  6. #4
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    Quote Originally Posted by POLECAT View Post
    ....I have found that it is best to position the fuel bulb in a vertical position when priming the motor with the end of the bulb that is closest to the motor at the top of its vertical positioning. That has always resolved the problem (for me) when a bulb refused to get hard...
    I never had to prime it this way until I replaced my fuel bulb with a Yamaha brand bulb and now I HAVE to do it this way.

  7. #5
    Dedicated TF Poster - Not a Tidal Fish Subscriber
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    I have the opposite problem. If I pump the bulb up until it's hard, my 8hp mercury wont start. I believe that it over pressurizes the float bowl and pins the needle valve closed. I usually disconnect the fuel line and run the engine dry after each use because I don't use the engine very often. When I'm ready to use the engine, I give the bulb a few squeezes until it just starts to firm up. It usually starts on second or third pull.

    I believe that one of the one way valves in your bulb is failing. Its' probably the one that is on the gas tank side of the bulb. To test it, leave the gas line disconnected from the engine and pump the bulb. If it still doesn't firm up then the one way valve is failing. If it does firm up, then perhaps the needle valve is not fully closing in the carb. And remember, if the bulb firms up during the test, it will spray gas when you attach the connecter to the engine so wrap a rag around it.

  8. #6
    Average TF Poster - Not a Tidal Fish Subscriber
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    [QUOTE=R&Jonthebay;3380021]I have the opposite problem. If I pump the bulb up until it's hard, my 8hp mercury wont start. I believe that it over pressurizes the float bowl and pins the needle valve closed. I usually disconnect the fuel line and run the engine dry after each use because I don't use the engine very often. When I'm ready to use the engine, I give the bulb a few squeezes until it just starts to firm up. It usually starts on second or third pull.



    I too have a merc 8 hp 2 stroke. If I over prime it blows it out of the fuel filter top. I always assumes it was a bad seal, now you got me thinking is supposed to do that...

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