I am looking at buying a 1996 420 Aft Cabin. The boat is powered by the base 7.4 merc engines which I believe are 340Hp each. The engines from service records have been well mainitained and have 635 hours. I boat on Lake Lanier, Ga. My question is: are those engines enough power for that boat? Seeing the configuration of how the engines are installed, if you had to repower or pull the engines for any reason, is it possible withoug doing surgery to the salon floor or cabin etc?