88' S24 performance

[SorrentoS24]

Hey guys I'm new to the board. I recently bought an 88 24' Sea Ray Sorrento. The boat had a reman'd 5.7L Crusader in it when I got it but when I took it out the first time i could hear/feel what sounded like a blown head gasket. I got it home, disassmbled it and I was correct. I went ahead and pulled the motor out. I disassembled the engine to inspect everything. I could tell it was recently rebuilt. The pistons are brand new as are all the bearings. I reassembled it to spec along with the new components, I put an Edelbrock Torker plus cam in it with new lifters along with an Edelbrock performer intake and a holley 600cfm four barrel carb. All new gaskets and seals. I checked all the valves in the heads and also installed Viton oil seals instead of the crappy o-ring type seals that were on it. I did away with the factory Mercruiser Y-pipe and plumbed a set of 4" thru-hulls under the swim platform with Hardin Marine stainless tips with internal flappers. It's nasty loud now but I like it. The engine runs good but I found it ran best with the timing set at 0 degrees at idle instead of the 8 degrees BTDC that mercruiser specifies. It has a 22 degree timing advance module. Anyways, the boat came with a small diameter 17" pitch stainless prop. When I took the boat out I was getting roughly 30mph at 3500rpm. This seemed like alot of RPMs for going so slow. I put on a larger 14.5"x19" alluminum prop that I had sitting around. The boat gets out of the hole just fine but I can only get 4000rpm and roughly 38mph on GPS with the current setup. I'm thinking maybe the engine needs more timing. With the base timing set at 0 degrees that would mean I'm only advancing 22 degrees at WOT. I'm wondering what kind of performance other S24 owners get. I cant imagine my engine setup being less than 300hp right now. It was rated at 270hp with the stock cam,cast iron intake and stock exhaust. Compression is 160psi on all 8. I can hear the vacuum secondaries open on the Holley around 3500rpm and all I gain is 500rpm...? The alluminum prop helped out with cruising as I was getting a steady 30 mph on GPS at 3200RPM. The Torker Plus cam I installed is good from 1,000-6,000 RPM. It has .488" of lift on intake and exhaust so I don't think it is lacking there. Maybe I'll take these heads off and port and polish them. I was hoping to at least have a 45-50mph boat. Any help from any other S24 owners with be greatly appreciated. I love these older Sea Rays, they are timeless.


P.S. -- It might all just be in my head. The boat I owned before this one was a 19' Action that ran 104mph with a 260 Merc. Not practical for anything but going fast and looking sleek.