Outdoor Power Equipment and Small Engines - Noma snowblower stalls

i have a Noma Canadiana snowblower, Signature Series 12/33,about 12 years old, not used much. Upon starting, it runs okay for 15 minutes, then starts running rough, and dies suddenly. The longer i leave it sit, the longer it will run upon restarting before it quits again. The only way it will run decently at all, even for a short period of time, is to set the choke on. Gas will run out of the carb at times. It runs much longer if i run at half throttle, so definetly a gas problem. Taking it to be serviced hasn't helped, as it can be coaxed to run okay , it's only after 15-20 mins of work that it dies, and garages aren't going to work it til it shows its syptoms. This blower worked okay for 2 years, and has given me grief the last 10 years. It is winning the battle. Help!

Your carb is gummed up. It needs thoroughly cleaning .
After setting all summer, carbs gum up. This is a very common problem.