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max-on 07-21-2007 10:32 PM

Outboard Stalling
I have a Tohatsu 4 stroke 6 hp outboard for the dinghy. Last year the engine ran great no problems. This year, it has started to stall when idling, and it 'sputters' when you initially increase throttle from the idle. It has new spark plug and new fuel filter. The gas in the tank is new also, with the proper octane rating. It seems with the throttle on revving high, either in neutral or in gear, it is fine. What is the best way to determine the problem.

mangomike 07-23-2007 10:58 AM

Hi…. my guess would be carburetion, of course that's always my guest. One of the most frequent problems with any outboard is the carburetor. All the little jets, and passageways means that any little microscopic piece of dirt can give you problems. I would start out with using some spray/liquid carburetor cleaner before taking it all apart. Also, if you do not have an in-line fuel filter I would suggest adding one of those. I in-line I mean, somewhere in between your gas tank and engine.

heinzir 07-23-2007 11:21 AM

Check the fuel line connections at both the motor and tank ends. I have had several OMC outboards that would stall and die for no apparent reason. Turned out that the quick connect fittings had worn and did not always seat properly, allowing the system to suck air.


max-on 07-23-2007 04:46 PM

Thanks for the suggestions, I will try the cleaner next, and then check the fuel line connections.

The motor does have an in-line fuel filter, which I replaced Saturday, although it was replaced already end of last season. That did not seem to be it as it stalled out again.

I'll clean the carb and take it out for a long ride at full throttle.

SanderO 07-23-2007 08:24 PM

You might have a fouled part in the carb. My 2 yr old 4 stroke Honda had some part destroyed by ethanol. The repair shop tried to clear the gunk or whatever blocked the passageway.... a very small diameter tube. They couldn't.

My engine would idle but I could not throttle up... it would sputter and stall. I replaced the carb and now it runs like a charm.

You should add a water fuel separator AFTER the bulb on the fuel line.

I was told to not store lots of fuel, use it and refill with fresh gas, and add fuel stabilzer. Apparently ethanol is wrecking lots of engines. I am not sure if it is worse for 4 strokes... but it hit me and I babied the motor.

I'd bet the carb fuel line is blocked.

sv shiva

sailingdog 07-23-2007 08:39 PM

I'd also recommend the Water/Fuel separator filter. I have one fitted on my boat, which uses a four-stroke OB as the primary engine. The filter I have is a Racor RAC052. It is fairly small, but does filter and separate out water, and has a clear bottom housing, but no bleeder valve.

max-on 07-23-2007 10:07 PM

I will look into the carb and line, thanks; I am thinking it is something with the carb. I have the standard nissan/tohatsu fuel filter in the outboard; so I should have another water separator filter, wold that be placed between the bulb and the connection to the motor?

I have not been adding stabilizer to the fuel, maybe I should. Thanks for the recommendations.

SimonV 07-23-2007 10:41 PM

Sounds like you put it away without running the fuel right out; over time the old fuel evaporates and turns into gum or a varnish like substance. The carb is a simple set up, pull it apart clean and refit. There is a blue coloured tube coming from the lower part of the engine connecting at the top of the carb. It is not a fuel line. This has a habit of hardening and cracking near the top check that.

max-on 07-24-2007 02:07 PM

That I do not always do, so could be. Thanks

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