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1998 9.9 hp Stalling after idling for a while

KR26

New member
Just got a 26’ Sailboat with a '98 9.9 Yamaha. Prior owner said it had the carb replaced and engine tuned up a few months before purchase. Shortly after purchase I motor sailed it for several hours and engine would run ok.
Starts fine after a couple of tries; However, if I leave it idling for a bit (several minutes), and try to accelerate it will stall. A few days ago, I was taking the boat from the boatyard to the marina and could not keep it running or accelerate. After many attempts I was able to make it run if accelerating slowly and restricting the air flow to the carb until it reached high RPM's.

Yesterday it had the same symptoms; when I removed the cover, the engine would run fine. Once I get it to accelerate it runs OK with no misfire or roughness.

Checked plugs and fuel filter and those are OK. Resistance for the Thermo-electric valve (starter) read 10.4 ohms.

Any suggestions?

Thanks!
 
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