How about 625 Vipers? My buddy has the identical Daytona as mine, he has 625 Vipers and I have Merc. 525's and he runs a good 15-20 m.p.h. faster

While a Pair of 625's would be nice. I havent seen too many of those on the used market place.

Merc 525 FTW

I think that removing the HO's and replacing them with anything other than 525's, Ilmors, or higher powered Merc products would be a mistake. HP500's and 540's while more powerful than 496's will always make a buyer wonder about who rebuilt them and how much life they really have left. With a 525 the reliability and power are well known. I have been trying to sell my 28 Daytona for 2 years and I think the problem is not so much the boat but the market. Nothing is selling, not boats, not houses, not cars. The only thing that moves is what is priced below market.