SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 460junkie on July 13, 2010, 01:35:49 AM
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I am in need of some helpful advice! Owner of a 21ft day cruiser and currently on my second rebuild. I am on a quest for higher rpm's, approximately 1000 more. Boat seems to reach around 4500 max rpm's, but what now?
Engine set up:
BBF 460
Sleeved, Bored .30 over
Stock crank and rods
Edelbrock carb 750 cfm
Edelbrock Performer RPM Aluminum Heads 75cc
Edelbrock Performer Aluminum intake manifold
Trick Flow Roller Rockers
Comp Roller Cam, Roller Lifters, Pushrods
Melling High Volume Oil Pump
Miloden 10qt oil pan
Jet:
Berkley 12JC, Aluminum A impellar
Hydraulic Place Diverter
Stock loader
I know the added length and weight being a day cruiser limits my power. Should i concentrate on my jet? Add a snoot,shoe, different impeller??? I really would like to surpass 5000rpms. Any suggestions would be appreciated.
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More power.
How big is that roller cam ? Problem might be that your motor can make more power at higher RPM but cant make enough at 4500 to get past that point. Post up some cam secs for the experts and I'm sure they can tell if thats the problem.
Also, are you sure its an A impeller in there ? I think (if I remember right) 4500 RPM on an A impeller is only around 300hp. Maybe its been changed to an AA. That would put the motor up closer to 350ish hp. A smaller impeller (B or C cut) will rise your RPM, but thats not really recommended with a big heavy boat.
BTW, the size / weight of your boat makes no difference for RPM with a jet. Your only spinning a water pump. If you put your motor and pump in a smaller / lighter boat, it would still turn the same RPM. It would just go faster. ;)
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More power.
How big is that roller cam ? Problem might be that your motor can make more power at higher RPM but cant make enough at 4500 to get past that point. Post up some cam secs for the experts and I'm sure they can tell if thats the problem.
Also, are you sure its an A impeller in there ? I think (if I remember right) 4500 RPM on an A impeller is only around 300hp. Maybe its been changed to an AA. That would put the motor up closer to 350ish hp. A smaller impeller (B or C cut) will rise your RPM, but thats not really recommended with a big heavy boat.
BTW, the size / weight of your boat makes no difference for RPM with a jet. Your only spinning a water pump. If you put your motor and pump in a smaller / lighter boat, it would still turn the same RPM. It would just go faster. ;)
good info rite here
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FWIW, The biggest problems with more RPM may out way the benefits... :thumbdown:
You can run in to oiling issues, more fuel consumption and a lot more noise for maybe 3-4 MPH gains.. :sly:
If you make more HP there is a chance the boat will go faster, but every 100 HP will equate to less than 5MPH in my experience.
I would concentrate on the set up more than RPM. ;)
GT