Picked up boat from winter storage, they winterized it and did an oil change. Yamaha 150 4 stroke has 20 hours. Went out idled fine for about 15 minutes. Pulled a tube at low speed for 10 minutes. Then tried skiing. Boat motor would stall out at higher RPMs. Had to go almost idle speed back home. Every time I would get the boat up past 15 mph it would stall.