[CMcLean]

It''s a Magnum 28 trailer sailer (built in Australia) with a displacement of about 2tonnes (probably closer to 2.5t when my wife has loaded it up). I get 6 knots plus with plenty in reserve for pushing into weather. All the Magnums run 9.9 Yamahas although the new motors have the 15hp body and will no longer fit into the engine well.
I was recently talking to the owner of a 36 foot catamaran who just completed a circumnavigation of Australia and he used a single 9.9 Yamaha as his only motor and was pleased with its performance.