Bagman,
Most reputatble dealers would never install a motor exceeding a boats maximum HP rating, due to liabilities.
There are several problems that exceeding the maximum HP rating can create.
The first is called chine. This is when the bow starts to dance from side to side at the higher speeds the larger motor may provide.
The second problem would be if you were ever stopped for an inspection by any of the agencies patroling your waters. They may cite you for exceeding the maximum HP rating for the vessel.
Also god forbid if you were ever involved in an accident on the water, good luck with that one if there were injuries and it went to court.
Happy boating,
Susky Kid