In the Final analysis its an individual decision and responsibility...there can be no one fit all solution or formular.
For a myriad of reasons.
That's why you should negotiate with you're insurer on an individual basis,and not take things for granted.
It is certainly beholdent to each owner to spec and INSURE his own Rig to suit his own needs,both in a Safe and Legal way!!!....
AND..Doing enough homework to make sure the chosen setup (Hull-transom-weight-power ect)...will actually stack up!
Things change all the time and the power plants (or ratings!) used these days in no way compare to those of the relativly recent past...whith many boats sporting power plants Vastly more powerfull than before.
With no detrimental consequences at all!!...unless it's to the pocket
Like I said this been gone over before(see previous threads)..and I'm sure will again!
Be safe and enjoy!