Idle issue on 2004 Yamaha F40?

[andymach23]

I had my 2004 F40 (15 hours run) idling at a steady 800 revs on the flush muffs in my yard a few weeks ago. The engine always starts without having to lift the fast idle lever.I went for a run yesterday and after cruising for 45 mins or so I brought the engine to a very slow speed. Just in gear with minimal throttle. The motor stalled and wouldn't restart without the fast idle lever being lifted.A while later I was idling in neutral and the motor's revs dropped to 600 after about 30 seconds or so and the motor stalled. I again had to lift the fast idle lever to get it to start.The only thing I have changed since it idled at a steady 800 revs in my yard was to add some fuel stabiliser. My fuel is also fresh. (The Quicksilver fuel stabiliser bottle was opened a few years ago if that makes any difference.)When I started the motor from cold before setting out on this trip, the idle was strong at a steady 800 revs.I had the motor serviced in February, and its still virtually new with 15 hours only so far. Apart from this it runs very well.Could this be an adjustment that is needed to the idle or could the fuel stabiliser be causing this?ThanksAndy

[rodbolt]

hello it sounds like you have introduced a contaminant to your fuel system. you may try draning the carbs and flushing the system with fresh fuel. the open stabil may have contained trash/water.