Yamaha 9.9 4 stroke outboard troubleshooting

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ecoughlin

There are lots of skilled people on this site... I have a 1997 Yamaha 4 stroke that runs like a champ. Idles well when warmed up, and is trouble free except it is very hard to start. For the last 3 years it has been tough to start after a period of non use. This year I am noting a surging at lower RPM's. Although I am thinking fuel pump, there are so many other reasons why it might be starving for fuel. Of course when I think it is starving for fuel it might well be flooded. It uses no oil, and is well cooled. It has metal yamaha fuel tanks. What's up with this engine do you suppose? Thanks much. Eric
 
F

FP

googled answer

here is a link to a site that may answer your question
 
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Benny

Sounds like the carburator is gummed up.

When an outboard is to be laid up for some time all the fuel should be burned out of it by disconnecting from the tank and allowing it to run until it dies. The cure is to remove and dissasemble the carburator immersing all the metal parts into a cleaning solution and blowing compressed air through all the orifices. Unfortunately been there and had to do that. Your symptoms are mild so perhaps you can get it cleaned by adding a carburator cleaner to the gas tank and run the engine with it for a few hours. Good luck.
 

BrianW

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Jan 7, 2005
843
Hunter 26 Guntersville Lake, (AL)
Old Gas? Gas Tank Vent Valve?

When I bought my '94 Hunter 26, it had been set up for awhile and I had similar issues. One of the problems was old gas starting to varnish up. When I changed out the gas it cured the hard starting problem but I still had surging proplems after 15 minutes of use. I then discovered I neglected to open my gas tank vent valve located on my gas cap. I felt kinda stupid on the last one, but was relieved that I didn't have a repair bill. BrianW
 
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Eric

Thanks

Thaks for the replies. I have done well running out the old gas, and using Stabil and fogger over the layup time. But from the responses, I get the feeling that it is a clogging carb, and not a fuel pump issue. The tanks I have do not have a vent, but often I will crack open the cap. Again, I alternate when starting, thinking that it is starving for fuel, and flooding... Benny? do you recommend a brand of carb cleaner to try? Thanks again. Eric
 
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Islandjack

an astrological answer

I work on a few kickers every week, and this past quarter every hard start, roough run situation I've had was the float needle sticking. Its probably happened 4 or 5 in a row now. I pull the carb, shake out the bowl and blow out all the air ports, and it works every time. Never have seen the grain of sand, water drop or whatever on any of them. Am about to chalk it up to planet alignments. But the flooding bowl causes wierd things. One give away I figured out on about the third one, is the carb will overflow gas into the engine compartment when the valve is stuck open and the squeeze pressure will go down if its stuck open. If it is working right no gas oughta come out of the bowl much less the carb when the float valve is working. Its almost the only moving part in these little kickers so it makes sense thats where the weakest link is. Good luck Jack
 
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