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Old 13-10-2010, 04:11   #1
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15hp Outboard Problem

My 3 year old Yamaha 2 stroke 15 outboard is runnung terribly. Earlier in the season I used generic 2stroke oil, and the motor would just barely run, and not idle. I changed gas, used much better oil, took the carb apart three times and cleaned it, new plugs, and it is still running badly. It is at low spee, and idle. High speed is good. There are no needle valves in the carb, the only moving part is the float. Ego won't allow me to take it toa mechanic (yet). I can't find a carb bow up drawing online. Any ideas? Thanks.

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Old 13-10-2010, 04:35   #2
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15 hp Outboard problem

On the starboard side of the carb. close to the flange that mounts it to the intake, there is a plug that covers the low speed needle. Removing the plug will let you back out the needle and clean the idle passages.

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Old 13-10-2010, 05:39   #3
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Someone must sell a, not too expensive manual for your motor. I have a Merc and bought a 3rd party manual covering just about all their 2 cylinder, 2 stroke engines. Didn't cost a lot and has always had the drawings and instructions I have needed.

It is worth having one on board.
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Old 24-11-2010, 10:09   #4
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Not sure about your particular yammy but these engine have a cold start circuit that is controlled by a wax pellet. I kid you not. As the engine warms up the wax melts and allows more air into the cold start circuit. If the electrics fail in this circuit the wax won't melt and it will never idle properly.
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Old 24-11-2010, 10:40   #5
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Squeeze the bulb in the tank hose when it's idling.If it stalls it is probably the fuel pump diaphragm leaking fuel into the base.Diaphragm kit is about $25.

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