It's a 2 stroke 90 HP motor. If air is not the problem, not sure what else it could be. Boat was running great till I put fresh gas in...what other causes would there be for the motor to falter and die out when run above 3500 rpm? When I'm running it, just before it dies out, the motor sounds like it's racing up, like a whoosh sound, and then dies. This also occasionally happens when I'm simply running it at low rpm, but not always. However, EVERY time I run it fast, it runs for 30 seconds to a minute, and then dies....I then have to engage the clutch, put the throttle all the way high without load, and then start the motor, and gently coax it up. Thanks again for your help and advise!! I've added some fuel additive also after this started happening, thinking it may be water in the tank, but I don't think that's it..but then, I really don't know much about these things....