Reply To: Propeller Cupping – 38 Bayliner

[Steve]

Sir,

Are those the original propellers and were they adjusted when the boat was repowered?

I had my prop serviced by Wilmington Propeller Service in Southern California. Talking with numerous others (including a Long Beach Harbor Pilot who has a fishing boat a few slips down), Wilmington Prop Service has a stellar reputation in the shipping industry.

The owner there told me that generally all props in tunnels should be cupped. He explained that given the propeller’s close proximity to the hull, cupping helps reduce propwash against the hull and generally makes it run more efficiently. I doubt you’d actually even notice any reverse response.

If you take create a table of your performance numbers at varying rpms, your prop guy should be able to optimize your prop and calculate what adjustment is necessary, if any.

Whether the hull pitting was caused by the prop or not, it wouldn’t hurt to see what your prop service says about your performance data and the tunnel/cup question. (I’m assuming that your guy will be as competent and trustworthy as Wilmington Propeller Service).

Good Luck Sir