If the prop hits something or is run in sand there is a rubber coupler in the prop hub that can get spun. Once that happens the prop will quickly get progressively worse until it will barely function past idle. It’s a 5 minute fix for the chase boat to swap out the prop. If the engine seems to rev normally but you are getting minimal thrust that almost guarantees that is the problem. The initial hit to the prop could even have been on a prior charter or the hub can wear out from long term use. It should continue to function at idle.
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