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Yamaha 40hp Troubleshooting

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Yamaha 40hp Troubleshooting
I've got a friend that recently bought a 2 stroke 40hp Yamaha. It starts easily but then stalls out when you give it any throttle. I imagine it is probably the carburetor but could also be the fuel line, etc. For example, my 6hp Yamaha was doing something similar this Spring and I found a pin hole in the fuel line between the fuel filter and carb.

Will the connector on my 6hp fit on the 40hp? Just to take that out of the equation.

Anything else I should look at with these motors? Fuel pump? I don't think he has changed the plugs or fuel filter.

I'm having a bit of a moral dilemma with helping him with the repair as he keeps on saying, "maybe I should just buy a new one and sell this one to you". :)
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Re: Yamaha 40hp Troubleshooting In reply to
Two things jump out at me.

1) Fuel line issue like you noted
2) Clogged high speed jet

How long has it been since it was regularly run? Two strokes tend to stop working after not being used for awhile, even though they worked perfectly when put away.
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Re: Yamaha 40hp Troubleshooting In reply to
Is it best to soak the jet in a cleaning solution or do you need to physically remove the blockage?
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Re: Yamaha 40hp Troubleshooting In reply to
Kris Winiarski wrote:
Is it best to soak the jet in a cleaning solution or do you need to physically remove the blockage?


I always take my motors to a marine mechanic. Too many other irons in the fire to fool with motors. I let the experts tackle those issues because working on motors is one of my least favorite things. I just know that clogged jets has been a common cause of my woes in the past that are similar to the way your motor is acting now.

Eric
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Re: Yamaha 40hp Troubleshooting In reply to
Kris Winiarski wrote:

Will the connector on my 6hp fit on the 40hp? Just to take that out of the equation.


Yes the fuel line connector should be the same.

Otherwise I agree with Eric in that it sounds like a fuel issue and that a clogged high speed jet is the likely culprit. A spray or additive cleaner MAY clear the blockage if the blockage is due to fuel gumming. If the blockage is a small particle of foreign matter, the carb(s) will need dissembled.

Take care, Huntindave McCann Smile SHELL ROCK IA. ,,,,,, "As sailors grow older, the wiser ones move to smaller boats." Thomas Firth Jones, Multihull Voyaging
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Re: Yamaha 40hp Troubleshooting In reply to
I would check all fuel lines and connections. Then pull both carbs off full disassembly and cleaning. Then replace the fuel clean/replace filters and try it. I would also make sure you have spark in all cylinders. On the side of the engine there is a filter you can look in for sediment. I would put fresh gas in any ethanol fuel that gets exposed to air with pull water from the air into the fuel.
South Jersey
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Re: Yamaha 40hp Troubleshooting In reply to
What they said!
I'd first check the gas can for bad/old gas. Get a clean tank of gas if neede. And check the under-cowl fuel filter for crud first.
Then replace the fuel line & bulb.
Next, carb/jet cleanup, which I also leave to the pro's.

Or tell your buddy its junk, take it off his hands for $50, let him buy a new motor and then repeat above steps. :)


Carl
Mobile, AL
DHBP Member since 1998

"Life is too short to drink bad beer."
Disclaimer: This post and/or report is not a substantiation of or reflection on the true accuracy of the present surveying methods. It is only a report on or comment concerning local observation and/or results. Your results and observation may vary based on your location, local water conditions, food supply, weather conditions and migratory patterns "
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Re: Yamaha 40hp Troubleshooting In reply to
If it starts up easy. Sounds like it is getting fuel.
I would pull the fuel line past the filter then pump the ball. If you are getting fuel. Then it not a fuel line issue.

If you know how to rebuild/clean a carb go for it.
Even if you do not you can always try. Utube has a ton of videos.
When all else fails bring it to a pro

It could be a choke sticking, a float not working correct or a jet clogged.