I have a 2004 Yamaha 150 hp two stroke hpdi. Yesterday I used the boat for the first time this year. It started and run well for up to 2500 rpm or about to 8 miles an hour. The moment I tried to give it more gas to go faster the motor stalled and shout off. This happened on and on every time I tried to go faster. It could run forever at a low rpm. The boat was winterized by a professional Yamaha dealer last season. I appreciate all help. Thank you.