That surveyor was doing exactly what he should be doing- pushing the boat up to wot for a few minutes to:
1. Check to see that it reaches rated rpm
. If not the boat is probably overpropped and that is loading the engine
more than it was designed for.
2. Check to see if it smokes excessively at wot.
3. Check to see if it overheats at wot.
I wouldn't want a surveyor who wouldn't automatically do the above. Having said that you only need to run for maybe 5 minutes at wot. It is kind of like running your car wide open on a deserted road to see what she will do. But you don't drive that way.