1991 Yamaha 150 will not idle this season

proftomda

Cadet
Joined
Sep 11, 2010
Messages
13
Hi all:

I have a 1991 Yamaha 150 on my Grady White. Ran flawlessly 7 months ago when I put it up for winter. Over the winter season, did my usual stuff like clean the spark plugs and change the water separator and lower unit oil. Ran well on the muffs 3 weeks ago in driveway. Took it out 1 week ago on maiden voyage and she would not idle very long before shutting off. Had to run it at higher than idle rpm to keep running. High rpm operation appeared normal. Like that all day. Put her back in the barn and rebuilt the carburetors and both fuel pumps but problem remains. Fuel tank and all fuel lines replaced 1 year ago. Spark plugs are 2 years old. Thinking of changing the water separator even though new. Other than that, scratching my head. Any help would be appreciated.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1991 Yamaha 150 will not idle this season

check compression, spark , and timing
If all that is good then you are left with a fuel problem.
Either need to clean carbs better, adjust properly like service manual says(link and sync) along with other, or you have vacuum leak
 
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