1996 Yamaha 115 2 stroke stalling

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Jamiemcd03

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My Yamaha c115 is stalling under a load. I have replaced the spark plugs and it runs good at first then like crap. The motor will idle, but when I accelerat it bogs and chokes out sometimes. Once I get the boat on plane and traveling at full speed it runs fine until I reduce power, then the motor starts missing and running like crap. There is oil on the plugs, and I am very meticulous with my fuel mixture so I know that's not the problem. Please help.
 
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99yam40

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Re: 1996 Yamaha 115 2 stroke stalling

need to see if it is loosing spark at problem RPM, timing light hooked to the different plug wires is the easiest way.
Check to see what timing is doing while you are at it.

How old is the fuel?
Most of the time it is fuel related
carbs, pumps, lines, sucking air, water, etc
 
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Jamiemcd03

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Re: 1996 Yamaha 115 2 stroke stalling

Im sure it's fuel related. The fuel is not old, but the motor has sat up a long time, being run with ears in the yard once a year. I've checked the vacum lines and there seems to be no holes or leaks. It's not a preticular RPM I'm having trouble with, it depends every time some times the boat runs like a champ.
 
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99yam40

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Re: 1996 Yamaha 115 2 stroke stalling

"run once a year on the muffs" tells me you need to pull carbs and clean them properly and then readjust like manual says.
I am sure you have not drained the tanks and put in fresh fuel every year you start it for a few minutes, so mixing fresh with old just gives you a lot more bad fuel.

Also would be a good idea to clean and flush fuel lines and pumps, as anything that is in them will hit the cleaned carbs after reinstalled.
 
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Jamiemcd03

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Re: 1996 Yamaha 115 2 stroke stalling

I bought the boat from my grandpa and he run the motor off a spare tank and ran the fuel out of the lines every time, so I'm sure it has to be in the carb bowls. I'm gonna pull them and adjust them and see what happens. Worked on lawn mowers and four wheelers, but never a boat. What's the difficulty? And thank you for the help.
 
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99yam40

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Re: 1996 Yamaha 115 2 stroke stalling

Yamaha service manual will help a lot

or you can try and look at your library to see if you can find something on your model motor
 
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