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1975 evenrude 15 hp runs good in a trashcan but bogs when lake tested

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  • 1975 evenrude 15 hp runs good in a trashcan but bogs when lake tested

    I an working on a 1975 Evenrude 15 h.p. outboard motor. I have been trying to figure out why I can run in in a barrel/tank for 30 minutes or longer but when I try to lake test it it stalls and will not restart.When it is renning in a barrel it will run at idle and at higher r.p.m.'s but when lake tested it falls flat on it's face within 3 seconds of coming off idle. Then it will not restart unless I prime the carburetor. I have not been able to figure this out. I replaced the fuel pump and may have not done it correctly. All help is appreciated..

  • #2
    See if it will stay running if you squeeze the primer bulb. Doing that does what the fuel pump is supposed to be doing. In addition to the fuel pump, ANY air leaks in the fuel hose anywhere between the fuel pump and the level of the gas in the tank will cause what you describe.

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    • #3
      After FRs test, try to open up the rich/lean knob 1/2 a turn counter-clockwise. If nothing, give it another 1/2 turn. If no help turn it back to where it originally was. If it does help then you might want to do a proper adjustment. Let us know if it helps and we can help with that.

      The other test you can do in the trash can is a cylinder drop test. This is to confirm that both cylinders are actually firing. In a trash can you will never know since these things can run on one cylinder quite well, but they bog down at higher power requirements.

      So to test this. Fire the motor up and let it warm up. Bring it to a fast idle and with a pair of insulated pliers pull one spark plug boot at a time. Do this for each cylinder. The motor should stay running. If the motor dies when a spark plug boot is pulled you now know that the other cylinder was not firing or is very weak.

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      • #4
        Those wee fuel pump all look the same but they are not.-----Take a look as there is an " up " marked on it.-----And they can be assembled in a different configuration too.-----The fuel pump is driven by a Positive pressure pulse and a slight vacuum pulse.-----There may be issues there.-----Test run with another tank and hose.-----Then there are some issues with the early 9.9 / 15 models as well that can be discussed later.

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        • #5
          any chance the float is not adjusted properly …. the inclination (angle) on a transom may be different than a barrel installation

          is the fuel supply in the barrel the same as in the boat ? (portable tank vs boat fuel tank with bad hoses , bad pick up or bad vent ?

          use the same tank that you use for barrel testing since you know that works leave the tank on a back seat in case the pump is weak and can't pull the gas.

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          • #6
            Where are you placing the tank when testing in a barrel? If it is above the motor, gravity works and it will probably keep the carb full. In the boat its probably below the motor so you need a working pump. I had that happen once,
            1976 Evinrude 9.9
            1961 Evinrude 18 hp

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            • #7
              If it runs ok in the barrel but not under load its your carb adjustments. Pull carb out and clean it and do a kit. link and sync it. Then turn attention to adjustment knob on front. This is VERY important. My motor was doing the same thing and that's how I fixed it. How to is found here: http://www.leeroysramblings.com/Outb...0articles.html

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              • #8
                Originally posted by bwkre View Post
                Where are you placing the tank when testing in a barrel? If it is above the motor, gravity works and it will probably keep the carb full. In the boat its probably below the motor so you need a working pump. I had that happen once,
                My thoughts too. Also, if you ran it in the tank w/o the prop (I do this) it will rev up easily since you're not generating power and consuming only a trace of fuel. Per all the above, good pressurized fuel supply and a clean, correctly adjusted carb should get you going.
                '96 Larson 174 SEI BR. 4.3LX 4 bbl Weber s/n 0F786604. Alpha One Gen II s/n 0F709315

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                • #9
                  Primer bulb is hard or soft?
                  Running in a barrel with no prop isn't something I would do either.

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                  • #10
                    JD any updates to the above advice?

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                    • #11
                      Sign up today
                      Running any engine in a barrel al neutral or idle rpm and powering a boat at load are 2 different escenarios. If cleaning the carb makes no difference whatsoever, need to start electrical troubleshooting..

                      Happy Boating


                      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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