2013 Yamaha T9.9 sudden idle issue

vt17

Cadet
Joined
Aug 20, 2009
Messages
16
Bought engine new. Has about 300 hours on it I'd guess. Always runs on non ethanol.

It's been great ...no issues and has idled perfectly since new. Yesterday it starts running rough at low rpm and dies at idle. Higher rpm seem fine. At mid rpms it will drop to an idle then surge back up ...then drop again and keep cycling.

If I didn't know the history I'd say dirty carb. Since there is an inline fuel filter in the outboard and it happened so suddenly I thought maybe it could be something else?

Any other thoughts on what it might be or best diagnostic I can do before removing and cleaning the carb? I wasn't sure if this symptom could be related to a known issue with ignition electronics or something else. Thanks.
 
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