nitrochief421
03-12-2010, 11:54 AM
Hello to all, been lurking in the shadows now for about 4 months, reading and learning. First off Ive seen alot of nice boats from everyone and have picked up alot of good info. Ive always been a I/O guy but have always loved the jet boats since the time that my buddys dad brought home their 79 cobra with a 460, WOW what a ride. 20 years later the kids are grown up and I find that I dont need my 94 Fourwinns gas miser anymore, especially since they're not boating on my fuel anymore. After 15 years of racing injected nitro and supercharged alcohol dragsters on the NHRA circuit its time to kick back with the wife and have fun on the lake again.
In January I got rid of the Fourwinns and picked up a 79 16' Cobrajet outfitted with a 350 olds and Berkeley 12JF pump. The motor was toast, and the pump needed some TLC, the boat itself and trailer are in VERY good condition so 950.00 later its mine. Parts for the pump will be here Monday so now the pump will be 100%.
Now this is the part that I would like your opinion on. I can tell that most everybody on here is like me...there is no replacement for displacement...but, here is the motor thats going in. It is a 350 chevy high nickel large jounal block with special main bearings so we could run a small journal Luannatti crank, its a 350 that can run the RPM's higher than most 327's to be precise its a 331. Other goodies include,Crower rods, tapered wrist pins (for lighter reciprocating mass), dished Venollia blower pistons, Crower roller cam, Crower roller lifters, Harland sharp roller rockers, Crane stud girdles, Pete Jackson gear drive, Dart 2 cylinder heads, Edelbrock Victor Jr. intake, Paxton Supercharger and a few other goodies Im sure you dont care about. The motor itself really starts to wake up at about 2700 RPM thru redline at 9000 RPM, but because of the Paxton redline of 7400 Rpm, I keep it to under 7000. 15 pulls on the dyno netted 360 hp @5400 and 375 ft/lbs torque @ 5150. Base compression is 9.2-1 so this is all on pump gas. This years goals are to get it in the water have fun and then next year the second Paxton goes on which should net me 20 lbs boost total.
I have no idea what to expect out of this in a boat, I know that when it was in the car it was very content to cruise the streets or to pull the skin off your face at the track. Im hoping that it will still be very happy to cruise in a boat or to atleast run 50 mph and toss my buddy out the back....what do ya think is 50-55 mph realistic.
Here is another question, I know on our roots style and screw blowers that you can get to a point where all pumps (air or water) go whats called supersonic and will actually decrease in out put. Do jet boat impellars experiance the same? At what RPM range does this start to occur? As you can see from the motor info it will carry some ungodly RPM, maybe to much for the pump. I dont know thats why i signed up here.
I apologize for this being so long, I promise you wont see another like this.
the bridge is yours over and out
Ron Potter-AKA Nitrochief421
In January I got rid of the Fourwinns and picked up a 79 16' Cobrajet outfitted with a 350 olds and Berkeley 12JF pump. The motor was toast, and the pump needed some TLC, the boat itself and trailer are in VERY good condition so 950.00 later its mine. Parts for the pump will be here Monday so now the pump will be 100%.
Now this is the part that I would like your opinion on. I can tell that most everybody on here is like me...there is no replacement for displacement...but, here is the motor thats going in. It is a 350 chevy high nickel large jounal block with special main bearings so we could run a small journal Luannatti crank, its a 350 that can run the RPM's higher than most 327's to be precise its a 331. Other goodies include,Crower rods, tapered wrist pins (for lighter reciprocating mass), dished Venollia blower pistons, Crower roller cam, Crower roller lifters, Harland sharp roller rockers, Crane stud girdles, Pete Jackson gear drive, Dart 2 cylinder heads, Edelbrock Victor Jr. intake, Paxton Supercharger and a few other goodies Im sure you dont care about. The motor itself really starts to wake up at about 2700 RPM thru redline at 9000 RPM, but because of the Paxton redline of 7400 Rpm, I keep it to under 7000. 15 pulls on the dyno netted 360 hp @5400 and 375 ft/lbs torque @ 5150. Base compression is 9.2-1 so this is all on pump gas. This years goals are to get it in the water have fun and then next year the second Paxton goes on which should net me 20 lbs boost total.
I have no idea what to expect out of this in a boat, I know that when it was in the car it was very content to cruise the streets or to pull the skin off your face at the track. Im hoping that it will still be very happy to cruise in a boat or to atleast run 50 mph and toss my buddy out the back....what do ya think is 50-55 mph realistic.
Here is another question, I know on our roots style and screw blowers that you can get to a point where all pumps (air or water) go whats called supersonic and will actually decrease in out put. Do jet boat impellars experiance the same? At what RPM range does this start to occur? As you can see from the motor info it will carry some ungodly RPM, maybe to much for the pump. I dont know thats why i signed up here.
I apologize for this being so long, I promise you wont see another like this.
the bridge is yours over and out
Ron Potter-AKA Nitrochief421