Im new to powerboating ( all other boats owned were ski boats, inboards) and this is my first build and I was wondering what some of the motor experts think of this motor set up im doing.
First off I have a 23' checkmate persuader with a stock 300 horse merc 7.4.
I put a gps on it and got theese speeds.
first run : 62 and some change on gps, with a 23 p quicksilver cleaver.
second run : 66.5 in some chop with a 23p @4600 mirage plus and it held 65 nicely in calm water
Third run:68.5 in some chop, trued up the hull (bluprinted) and added a set of gill magnum choice manafolds and was running a 25p mirage plus @ 4200 and the boat held 66.5-67 in calm water.
the boat takes off from a dead stop to on plane in just a few seconds with lots of bottom end.
After I trued up the hull ( I own a fiberglass and gelcoat repair business) I used less trim. Before there was a rooster tail that was about 60'. after the work on the hull the roster tail was gone and the boat responded much better at higher speeds and felt like it was riding higher in the water.
We pulled the motor last week and tore it apart. I sent the block and parts to the machine shop to be balanced and have the bottom end put back together using the stock crank and rods, only replacing the pistons with new(flat top). The block is getting cleaned, honed, decked.
I am using the following parts for the rebuild:
1968 large oval port 396 closed chamber heads (to up the compression) There getting a valve job and resurfaced.
Cam- crane roller 553/576 214/222
hydrolic roler lifters (retro)
SPRINGS - Outer Diameter 1.540
Inner Diameter 1 1.140
Inner Diameter 2 0.760
Damper YES
Seat Pressure @ Installed Height 150 lbs @ 1.900
Open Pressure and Height 560 lbs @ 1.150
Coil Bind 1.085
Maximum Net Lift w/.060" Clearance 0.755
Average Spring Rate 528 lbs/in
Holly 750 marine carb
Edelbrock rpm air gap dual plane intake
crane roller rockers
crane push rods (13628)
Does this sound like a nice setup for a boat? What RPM's should I run to be safe? and what kind of power should I expect?
I got most of my info for the build from a local high dollar shop. the owner built a motor for his old boat using simular parts, he said it was dinoed around 500hp. Im not sure if this sounds right but what do you guys think??
Thanks for your help
Chris
First off I have a 23' checkmate persuader with a stock 300 horse merc 7.4.
I put a gps on it and got theese speeds.
first run : 62 and some change on gps, with a 23 p quicksilver cleaver.
second run : 66.5 in some chop with a 23p @4600 mirage plus and it held 65 nicely in calm water
Third run:68.5 in some chop, trued up the hull (bluprinted) and added a set of gill magnum choice manafolds and was running a 25p mirage plus @ 4200 and the boat held 66.5-67 in calm water.
the boat takes off from a dead stop to on plane in just a few seconds with lots of bottom end.
After I trued up the hull ( I own a fiberglass and gelcoat repair business) I used less trim. Before there was a rooster tail that was about 60'. after the work on the hull the roster tail was gone and the boat responded much better at higher speeds and felt like it was riding higher in the water.
We pulled the motor last week and tore it apart. I sent the block and parts to the machine shop to be balanced and have the bottom end put back together using the stock crank and rods, only replacing the pistons with new(flat top). The block is getting cleaned, honed, decked.
I am using the following parts for the rebuild:
1968 large oval port 396 closed chamber heads (to up the compression) There getting a valve job and resurfaced.
Cam- crane roller 553/576 214/222
hydrolic roler lifters (retro)
SPRINGS - Outer Diameter 1.540
Inner Diameter 1 1.140
Inner Diameter 2 0.760
Damper YES
Seat Pressure @ Installed Height 150 lbs @ 1.900
Open Pressure and Height 560 lbs @ 1.150
Coil Bind 1.085
Maximum Net Lift w/.060" Clearance 0.755
Average Spring Rate 528 lbs/in
Holly 750 marine carb
Edelbrock rpm air gap dual plane intake
crane roller rockers
crane push rods (13628)
Does this sound like a nice setup for a boat? What RPM's should I run to be safe? and what kind of power should I expect?
I got most of my info for the build from a local high dollar shop. the owner built a motor for his old boat using simular parts, he said it was dinoed around 500hp. Im not sure if this sounds right but what do you guys think??
Thanks for your help
Chris
