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We have a Honda GX120 engine attached to a 2'' water pump used to pump out the holding tanks of boats. For a while now when we start it will run for about a minute, start running rough and then stall out. It can be restarted again, right away, and the same thing will happen. We have installed a new filter in the tank, replaced the carburetor, removed the head to clean and inspect the valves (they look great) reassembled everything and the same problem exist. I don't know where to go from here. This problem started out slow and has gotten progressively worse to where it is today. After a few starts the spark plug is fouled black like it may be running too rich.

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The one thing you did not mention was the type of spark your recieving at the spark plug. I recommend that a spark tester be used, which can be purchased at an auto parts store. Set the spark plug tester gap for 10,000 volts, or a good 3/8". You should see a nice sharp blue spark. If you are recieving this kind of spark, then with valves closed or at top dead center apply 30 psi into the cylinder. This test will let you know if the valves are seated properly. If valves are not seated properly you will hear the air come out from the intake or exhaust. So, it is either your ingnition coils or warped valves.

Posted on May 07, 2009


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I was running in a tank my new 5 HP honda 4 stroke and it quit pumping water...and the water is well above the cavitation plate.There was a stream coming out higher up when I started it.

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Engine tank should be plumb full tight. The engine supplies about 2 lbs pressure through one of the 2 lines going to the boat tank. The other line takes the oil to the engine tank. If that line gets kinked or pinched, the engine tank won't get oil, a check valve lets a little air into it, and the oil pump keeps getting oil. When it goes down just a little, the alarm goes off telling you something is wrong.

Sludge in the boat tank could plug up the pickup screen. I've also seen them plugged up by a foil oil bottle seal carelessly dropped into the tank.

Once you find out why the oil couldn't get there, start the engine with the cowl off and loosen the cap on the engine oil tank until it leaks, then tighten it down and clean up the mess. That tank is normally plumb full tight.

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Are you sure you don't have a 2001 Bayliner Trophy? ;>)

7 gallons, but they come in sizes 17 feet to 31 feet and 125HP to 225HP.

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Easiest way is to run it dry with a 1 gallon portable can on board. Stay close to the marina until main tank runs out, top up with the gallon can, and then go to the marina and fill it up. Whatever it takes minus 1 gallon is the capacity. Then refill that gallon can and log how many miles you do on a full tank. I carry 2 x 6 gallon tanks, I know one tank will take my 95 kilometres (I am in Canada)

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1 Answer

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There are only 3 things necessary for ignition.
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Use a starting fluid spray directly into air filter.
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remove the carburetor float bowl and then use a screwdriver to remove the jet locking nut in the tube the bowl nut attaches.
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If engine doesn't start check for spark either using a spark tester or removing the spark plug and holding plug against the engine frame and pulling starter rope if spark is present replace the spark plug and try to restart the engine.

If these steps don't work I would replace the carburetor.

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1 Answer

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1 Answer

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1 Answer

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1 Answer

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