6hp Tohatsu having problems

I have a 6hp 4-stroke Tohatsu that has been very reliable for almost 5 years. That is until last week. Problem now is; It will only run for a few minutes after starting, then stalls out. Has a lot of trouble restarting and sometimes won't restart until I try it again the next day. It won't settle down into a good idle. I have to throttle up to keep it running and then, it stalls in a few minutes. It stalls quicker under load. I suspect fuel problems but I need to know where to look. The engine sometimes sits for weeks without use. It gets used by others besides me so it gets shut down differently every time, some pull the lanyard, some pull the fuel hose and some pull the choke to stall it, its never been a problem. It gets stored all winter but started up and ran fine earlier this summer. The tank does have fresh gas. Oil level is fine; between the marks. I'd like to fix this myself, the boat is 40 miles east, and service is 40 miles west.

Could be a number of things, likely fuel-related. Odds are that the carb has varnishing problems. You MUST disconnect the fuel and let the carb run dry at the end of every day. Otherwise, if fuel sits in the carb, it will evaporate, leaving a varnish residue that is difficult to clean out of the tiny carb passages. Also, water and/or ethanol (present in many fuels), if left in the carb for long periods of time, will result in corrosion in the carb, which cannot be cleaned by ordinary means. In some cases, I have had to replace these carbs due to those oxidation problems.

Thanks, you confirmed my assumptions. I was going to pull and clean the carb but I wanted to hear from someone that I was on the right track. I'll tell my low life partners to shut it down correctly from now on. Now I just have to explain to my wife why I have yet another carb torn down on the kitchen table. (Yes, it happens a lot.)

If you want to do a proper cleaning, you will need to completely disassemble the carb (jet and nozzle, etc.), and soak it for 4 hours in real carb dip. Spray cleaner will not be aggressive enough to clean the varnishing from the small passages.