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Old 03-02-2014, 12:56   #16
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Re: HELP: Yamaha 4hp outboard engine

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Originally Posted by beneteau-500 View Post
I have the same 4hp engine one thing with these engines for some unknown reason is the float valve jams fully open indicating fuel bowel chamber is full i found by slightly moving the float pin over the one that the float swings on one way fixed the prob and the second prob it might be is the kill switch one way of testing this is to disconnect the white wire near spark plug and see if she starts
I would second this and from what you were describing.

When you remove the drain on the bottom of the bowl, you should get more than a little bit of gas coming out, especially if the fuel line is still attached.

If you carefully remove the float bowl, you can check the needle valve goes in and out when you raise the float up and down. blow in the fuel intake and lower the float down and you should hear air come through. Spray with B12 or other carb and choke cleaner while the bowl is in the down position and put back together.

Put your hand over the intake and pull once in order to pull gas into the bowl. Next choke it and start.

Use Seafoam in your tank. It does a good job at liquefying gunk.
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Old 03-02-2014, 14:21   #17
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Re: HELP: Yamaha 4hp outboard engine

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Originally Posted by myocean View Post
Thanks for all your hints!!
Yes, it was very old fuel, but I don't think with Ethanol. Anyway I have replaced it by new fuel and the engine still won't run.
I found that the carbs 'cup' did not even get wet anymore.
I found a nice guy here in the bay, boatbuilder, who knows a lot about engines and he helped me to get this solved: The inlet valve into the card which gets actuated by the float was blocked by a little tiny black piece dirt. This must have ended up there after the reassembly of the engine in the service.
Now its all up and running again and - may be even more important - I will have no problems to solve such issues by my own in future because I have learned a lot!
Congratulations!! I'm glad you got that one solved and I'll bet you're happy it is pushing you around again.

That's all it takes is just a little bit of dirt in there.

Be certain you don't let any ethanol fuel stay in your carb. It'll gum it up much worse than the little spec of dirt.
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Old 22-02-2014, 14:02   #18
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Re: HELP: Yamaha 4hp outboard engine

Be very careful with the gas and tank. I have a 8 hp 4 stroke, every spring I have to get the carb cleaned, a small piece of dirt or hose gets in, and the low speed jet is VERY tiny. It plugs just from thinking of it. I have double in-line filters, still plugging. Took extra precautions last fall, will see in a few months if prudent.
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Old 22-02-2014, 20:57   #19
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Re: HELP: Yamaha 4hp outboard engine

That black piece of dirt, you saw could very possibly not be black dirt. The ethanol in the gasoline breaks down the inside of the hose and it begins to fall apart in little pieces. Those pieces flow downstream. That might be what you found, which means you need a new hose.
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Old 23-02-2014, 11:36   #20
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Re: HELP: Yamaha 4hp outboard engine

Oh, interesting input! Thanks!
Right now it works fine! I had already exchanged some hose sections as they broke so easily.
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