Keep in mind I've only used the boat 5-6 times since purchase thanks to Hong Kong's stringent operator licensing regime. When I did the sea trial with a clean hull, I saw similar result to Michael on SM251: wide open throttle gave me about 7.7 knots in flat water @ 2600 rpm. It was running bit hot though. As the propeller started getting growth, she started moving a LOT slower under engine. I hauled out a week or two ago and had a small coral reef growing on the prop and c-drive.
I've just reduced the maxprop propeller pitch from 18 degrees to 16 degrees based on the advice of the engineer that installed the Beta, which will of course reduce my top speed but also reduce load on the engine. Will see how that goes.
More power would always be nice, but it comes at a cost in terms of fuel consumption, weight, engine complexity (turbo!), and money. If I was doing the re-engine myself, I'd seriously look at the Beta 85T that Bill Rouse recommends. That said, I might still end up with the Beta 60 because I find myself leaning towards smaller engines in sailboats. The goal is to sail, not make lots of noise and burn up lots of fuel to push 16,000 kg 1 knot faster.