with out getting personal.(like some)
and i'm insured aswell 2millon liabilty
I very much doubt that your insurance company would cover you in the event of a serious claim. Any claim that involved investigation (injury, death, total write off) would quickly show the boat was not being suitably powered and your 2 million cover would simply end up being that you owe £2 million to the family of the person you've just killed as the insurance company would wag a finger and walk away.
The manufacturers limits are set by them for a reason. Not just for fun.