Tuning a feathering prop

I have owned Alestra a 25ft Jaguar for four years. The previous owner had re-engined the yacht with a 25hp Beta Marine unit and in 2013 fitted a Darglow Featherstream propeller – an impressive set-up for a 25ft yacht. This propeller has blades that feather while sailing, which reduces drag.

I had always felt that the engine was underloaded – at full speed it