close

Privacy guaranteed - Your email is not shared with anyone.

Fuel System Question

Discussion in 'Boats and Motors' started by OSU_Fisherman, Apr 23, 2008.

  1. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    Got the boat out today to make sure it was going to run correctly, and at first it ran amazingly. We ran in the 50mph range for around 10 minutes so I was convinced all my problems were solved. So, we fished for a couple hours... and mixed in a couple slow runs in the no wake zone out at Oshay.

    When we were done fishing, we went to run back, and the motor started acting up again. We got on plane, and got up to about 51 mph for a bit and the motor started to struggle and slow down. When I backed out of the throttle, it sped back up only to slow back down. I tried to run it strong a few more times, but the motor seemed like it was struggling for gas after it got over 25 mph. Both tanks had more than 10 gallons of fuel in them.

    I just changed the fuel and water seperator 2 days ago, and the spark plugs only have a few runs on them. Where do I look next?
     
  2. If this is a carbed engine, you may be losing prime, or problem with the air/ fuel mixing.
     

  3. Have you ever redone your carbs?
     
  4. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    No, I have not redone the carbs. I just bought it this past off-season so I haven't had it too long. I was hoping to not have to mess with the carbs since there are 6 of them.
     
  5. freyedknot

    freyedknot useless poster

    does the primer bulb get soft? next time it wants to die out pump the bulb and see if that helps. it may be bad ,or the fuel pump.
     
  6. fishingguy

    fishingguy The Inferior Fisherman

    I agree with freyedknot. Also is there a filter somewhere along the line. I had a motor that someone stuck a extra filter on the gas line. How old are the tanks? Sediment in the tanks could cause the problem also.
     
  7. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    The primer bulb does get soft, but I believe it has done that even when it ran correctly the first couple times I had it out. I usually have to go back and pump it again if the motor doesn't catch on the first couple tries after sitting a while.

    I had assumed that the fuel pump was to blame, but I have received conflicting answers from the same local repair shop. One guy said there is a seperate fuel pump and they make a rebuild kit because the diaphram inside the pump likes to crack sometimes. The other guy said that the only pump on my motor is the VRO... which can only be replaced at $360+labor. Which is it?

    There is an inline filter in the motor that I might have to take a look at. Also, the fuel tanks are the original ones from Ranger that came with the boat in '89. What can I do about sediment? Do repair places vacuum out the tanks or something?
     
  8. fishingguy

    fishingguy The Inferior Fisherman

    I would replace the filter, than get a good 6 gallon tank and put some fresh gas and oil if needed, and go out and test it. If it runs good, you know the problem. If not, than proceed from there.
     
  9. If the filter doesn't take care of it, change the whole fuel line and primer bulb. Relatively inexpensive. Use only the original manufacturer's equipment (OMC, Merc, etc.). Do not buy that cheap Atwood stuff they sell at Walmart. Just asking for trouble. The hose will get brittle and crack, and the primer bulb will get hard like a rock in a year's time.
     
  10. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    Went to a local boat shop today to pick up some supplies for trying to fix my boat. I originally went in to buy an inline filter, fuel lines, and a diaphragm for the fuel pump in the VRO. The only thing they would sell me was the inline filter.

    Through my conversations with several techs, it sounded like they had no desire to mess with my VRO if it ends up being the problem. It sounded like the only thing they wanted to consider was removing the VRO, slapping in a fuel pump, and having to pre-mix. Any Thoughts????
     
  11. Marshall

    Marshall Catch Photo And Release

    2,114
    159
    1,348
    Sorry to hear about all your problems, hopefully you will get them all worked out. I feel your pain.
     
  12. Which shop did you visit, and what make is your motor? I'd try Paul's Marine first (closer) or Knox marine. I would think either shop would sell you anything you were looking for.
     
  13. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    For some reason I feel like a big part of it was that they sensed my confusion in what to do. I think that when I try a few things this weekend and I can go back there with a little better idea of what is going on they'll be willing to play ball. They knew I was taking a stab in the dark haha.

    Its an '89 Johnson GT150 motor.
     
  14. UFM82

    UFM82 The one others want to be

    2,081
    311
    1,268
    Primer bulbs do NOT stay hard after the engine is running. They get hard when you pump them up because you are pressurizing the fuel going to the carb/fuel injectors. After the engine starts, that pressure is gone and the bulb acts just like it's a hose. The fuel simply passes through. If you squeeze ANY bulb after the engine is running it will feel soft. That's normal.

    On a Johnson VRO pump there is indeed a diaphragm for the fuel pump side. There is also a diaphagm for the oil side. If you were to take the pump off the engine and open it up, you'd see the two "halves". It's very possible to have a weak fuel pump. However you may also have an intermittant blockage or restriction. If access isn't too awful, I'd eyeball every inch of hose from the tanks back to the bulb. Also, if you have access, it may not be a bad idea to pull the pick-up tubes from the tank and check them. Sediment may be an issue on an older boat. The boat ran well at first because the sediment had settled and didn't get in your way. Then it was disturbed and caused issues.

    I'd bet on a fuel pump myself barring everything else. You can tel lfor sure by using a small 2 gallon tank, strap it to the top of the engine and run it that way. If the run issues go away, fix the fuel pump. Sounds silly but it works.

    UFM82
     
  15. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    Wow, I am so close to having this thing fixed I can almost taste it.

    I switched out the in-line filter and added some Johnson/Evinrude fuel treatment. I ran it 2 days ago and it ran perfectly to and from the spot we fished out at Oshay.

    BUT, today my fuel was running low in the Starboard tank after a perfect morning run, so I switched it over to the Port side tank as we were coming back from the South end of the lake close to the dam. Again, it was starving for fuel at speed and idling rough. This got me thinking.... and I seem to recall that EVERYTIME I have had trouble with it running... it was out of the Port side tank.

    So now I guess I have it narrowed down at least. Main problem now is that I have no clue how to access my fuel tanks as they're built into my boat. I was told to check the anti-siphon valve at the top of the tank, but I've got to find it first haha. From there, I'm guessing all I can do is check the pick-up hoses, fuel lines,... anything I'm missing?
     
  16. Not knowing what type of rig you have, I'm guessing to check not only the anti-syphon valve, but any fuel lines from that tank as well, they may have collapsed or kinked in some way. Hope this helps.
     
  17. UFM82

    UFM82 The one others want to be

    2,081
    311
    1,268
    It's not the anti-siphon valve, it's the tank vent. Find that and clear it and you'll most likely be fine. Spiders, wasps and other critters like to get in that vent and make homes and it blocks the passageway. Run a small piece of stiff wire or something in the vent and clear it. That should cure the sputtering blues. A clogged vent will make an engine behave just like a weak fuel pump because it will starve the engine of fuel as a vacuum is pulled in the tank.

    UFM82
     
  18. also when you check the vent line make sure it does not have any big dips in it ,,,I also am sure the vent line is your problem,, it happens all the time
     
  19. I just noticed this thread or I would have posted sooner. I had a very similar problem one day with my small outboard and portable tank. Turned out I had forgotten to loosen the tank cap when I went out. Running the motor had created a significant vacuum in the tank. When I did loosen the cap had a big whoosh as air rushed into the tank. Problem solved.

    I also suggest that you check your tank vents.
     
  20. OSU_Fisherman

    OSU_Fisherman Bassin' Buckeye

    806
    0
    371
    Haha, I guess its unanimous... I'll check it later today and hopefully try and run it again. I'll let you guys know how it goes.