Yamaha T9.9 idle and throttle problems- dies while idling.

[SenorFish]

Ok, so I took my carb apart and cleaned it up pretty well. My engine though keeps dyeing when idelling. If I give it alot of pumps on the fuel bulb, i can get it to idle for a minute or two. But, even so if I then try to switch in gear and throttle up, the engine dies again.

However, if I mostly cover the carb air intake with my thumb while idling up, the engine will accelerate without dyeing.

Are my problems related to an air leak spoiling the vacuum of the fuel flow? Is my engine running too rich or lean? Any help would be appreciated.

[Don S]

T9.9's have been around for a while, do you have a full model number?

[SenorFish]

I solved my problem after a few attempts. As I already mentioned, I took apart the carb and attempted cleaning with carb spray and small wires. This made a slight improvement- but not enough to run smooth. Second attempt, I took the carb apart again and removed all plastic parts (the bottle float was a little challenging to get off). I soaked it for three hours in carb parts cleaning (a gallon paint can with a dip basket, $30 at Kragen Auto). Reassembled and the engine runs like new. Definitely seems this problem is from gas sitting and varnishing in the tiny fuel parts inside the carb. Not an airleak problem like I was thinking.

In the future, what the best way to stabilize the gas/ clean the carb for storage? I would like a technique to do after each use as the boat usually sits for a month or two between outings. Gas addative? Drain the fuel lines? Soak the carb every year?