Tohatsu 6HP Hard Start & Sudden Shut Down

Outboard: Tohatsu 6 hp
Age: 2 years 3 months
Issue: in the last 4 months the engine starts after a few pulls and runs for about 5-10 minutes at full speed and suddenly just shuts down (once I believe I heard how it backfires, almost like I hit something). It's very hard to start after it happens, and I usually wait for a minute or two and start it.

Also, if I stop somewhere after driving and the engine cools off decently, it starts under choke but about 10-15 seconds later revs high and shuts down. And it's very hard to start.

I decided to clean the carburetor and all jets (except pilot jet), change engine oil, change spark plug, float valve, fuel filter, manifold gasket between carb and engine, and it got a bit worse. The fuel tank and fuel line are a half year old and I'm using non-ethanol gas and recently started using stabilizer. The fuel bulb doesn't collapse and carb is about 80% full.

At this point I'm thinking to either replace the carb or buy first ignition coil, but they both are not cheap, so I'm hoping I can at least eliminate one of these . Any help is appreciated. If I don't replace the carb the next step for me would be to open pilot jet and clean it.

Assuming your model is MFS6C.
Sounds like fuel starvation.
What method did you use to clean the carburetor?
Your model does not have a separate ignition coil; it has a single-piece ignitor. They are crazy reliable, so probably not at fault.
If properly cleaned, the pilot screw seldom if ever needs cleaning; If you decide to do that anyway, be sure to count the current number of turns until lightly seated, and reset it to that setting after cleaning.

Yes I have Tohatsu MFS6CS.
I use a spray carb cleaner and soak the jets in it, and spray inside the carb and leave it for an hour or so.
Is there some kind of solution I can buy to soak in the whole carb?

Do an complete disassembly, soak all non rubber bits in real carb dip overnight, then blow out with generic carb spray. Then reassemble, paying close attention to float height. Then retest.

Thanks Paul. I soaked it over night for about 12 hours, and tested it at home and starting worked great on first pull without choke and with 1/4 throttle opened. I would start the engine after 2, 5, 10, 20 minutes no problem.

I launch today and drive 3/4 speed for about 10 minutes and it shuts down. After starting I decided to drive 1/3 speed and drove for about 30 minutes without shutting down.

I’m thinking to check the thermostat first.

Test temperature with a cheap IR thermometer. You could have a vacuum leak in the fuel system. Bad o-rings in the fuel primer hose connectors are famous for that.

Paul,

I have replaced the fuel pump, lowered engine oil to be between min/max position, and replaced fuel cap, and I my problem disappeared.