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    Propeller cavitates over 4000 rpm

    2000 Aqua Patio 210 with a Mercury 90 h.p. outboard.  The prop cavitates when engine is running over 4000 rpm.  The engine is mounted  in the most low position.  What prop should be used?  What is max rpm for this engine?  Thanks, Kenny


    • Capt_SteveCapt_Steve Member Posts: 164 admin
      @kenny131lt ... that motor would have had a 14x13 prop. Here's some info from Mercury site on RPM question: 

      My outboard does not operate in the maximum RPM range shown in my Operation, Maintenance & Warranty manual. What should I do?

      Mercury FourStroke outboards 20 horsepower and below come standard with a propeller that should meet the needs of most applications. However, there may be situations in which this standard propeller does not provide the best performance. In such cases, the propeller may need to be changed to a higher- or lower-pitch propeller. Generally speaking, a higher-pitch propeller will lower the maximum RPM that the engine will run at during full throttle, at the expense of a slightly higher top speed, while a lower-pitch propeller has the opposite affect (higher maximum RPM, but slower speed).

      Above 25 horsepower, the variety of boats is much greater and therefore, the propeller must be purchased separately to match the boat’s needs. The Mercury Prop Selector can give you suggestions on a propeller for your boat type. Or, you can consult your local Mercury authorized dealer to ensure you have the best propeller for your boat.

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