My understanding is weight hanging off your backside is the actual
problem, if your transom is designed for 200kg, but you throw a
250/300kg motor on there, then during deceleration or big bounce is chop
the amount of strain the rear of the boat undergoes is massive.
Basic skipper skills.. Never travel at speed, then pull back the throttle fast..regardless of what grunt on the back, the hull stops fast and the following wake will come over the transom
.
As to weight.. you may put an OB on the back in spec.. then start adding tuna tubes, live bait, extra battery, a bucket of water to drop fresh catch in and 3 burly guys fishing off the back.
If bit over powered , and over weight which I am on my old commander with a V6 150hp..
common sense comes into play.. dont be a bloody boy racer in a supped up boy racer car and havnt attended to good tyres and brakes...
Insurance, think they will have something to say iif miss use the power and hull causes an issue.. where it doesnt.. maybe not.
Also a thread few yrs ago discuses a member here who paid a little extra for a replacement 'upgraded' tag on the boat ...