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I need some help. While driving my 21' pontoon with 97 90hp evinrude. When getting into med rpm range the motor revs up and doesn't change speed. Figured spun a hub. Put brand new prop on and still does it. This isn't a constant problem. Comes and goes. Feels like something is slipping. Any help???
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Prop may be ventilating, trim motor down to see if helps or move everyone onboard to back of boat to push prop deeper in water. Look for something loose on boat in front of outboard disrupting flow of water to prop. -
Motor is trimmed all way down. I looked under boat while underway from front. Seems to be a big ridge of water half way back. Could be affecting water around prop. Causing ventilating. Would a hydrofoil help if that is the cause?Comment
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Hydrofoil don't normally work well on a pontoon boat. Did anything get added to boat that may have caused this like a transducer?Comment
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Prop is definitly cavitating (proper term), which would cause overrevving (as prev mentioned, it's creating an air pocket and spinning in that air under water.) Trim and shaft length very important for pontoon. Trim can change with guests moving about. I have 24 Footer and like an airplane, have to adjust trim almost constantly. Down causes bouncing, up causes cavitation. Try some guests in front, then attempt trim.Comment
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