I have a 30 hp on a pontoon boat that runs good until you goto open it up. At this point when you hit about half throttle the motor begins to red line or close to max rpm,s. I have removed the prop and marked the hub and reinstalled it and run it again to see if it is the hub that is spun. But this is not the problem. Does anyone have any sugestions for me? thanks much for your time!!
<br /><br />Sounds to me like your prop is ventilating or cavitating.<br /><br />Inspect the blades for bends or chips and check where your AV plate is relative to the bottom.<br /><br />Good luck.