With aftermarket camshaft 5K is a little low in my opinion for a BBC....I would shoot for 5500 or so.

It is my impression that if two 600 hp motors cannot reach their peak performance because of too tall of gearing then they are straining and could break.... If red line is 5600 and the rev limiter cuts in at 6000, then I would think the proper props would allow me to reach 5600, maybe even slightly more.

Here is the question - what prop should I use? Anyone know what the mathamatical formula is?

31 ft 7500 lb CAT with two 600hp CBB's in it with a possible 5600 rpm and a 1.36 ( 1.35 something like this) gearing.

Rick

Hey Rick

Griff graciously posted the calculator in your other thread...

http://www.offshoreonly.com/forums/p...e-props-2.html

0r

http://go-fast.com/Prop_Slip_Calculator.htm

With 1.35 and 28 pitch 5600 rpm yields theoretical 110mph applying 7% slip is actual 102 mph which is about what the previous owner indicated.

With 1.35 and 24 pitch 5600 rpm yields theoretical 94mph applying 7% slip yields actual 87mph.

Not sure what prop you should run but this should help you determine your speed if you can make 5600rpm at the lake.
I like to balance my cruising speed/RPM with WOT speed..

Rick, I have run my Jag from Garwoods to Emerald Bay wide open with the wrong props without any engine damage. I usually run between 5800 and 6000 rpms and had the boat propped wrong and could only make 5000 rpm. I threw a blade and had to use a back up set. The motors just react with the larger pitched props by running with less rpm's and maybe outside of the power curve and the result is less topend and slower acceleration, not engine damage. Try Rob's props and for the money they will be very close. Again, the nice thing about Bravo 1 props is they are cheap and easy to swap or trade. I still have some props for a bravo drive but they they are Mach's 4 blade and Mirage 3 blade, both L and R's that I would sell cheap, but I don't think they would fit your application. Good luck and I sure wish spring would get here. Call me if I can help. 916 539-2540. Doug

Couple things to note... Doug's engines are supercharged , therefore will make more torque when "lugged". Your N/A motors will have a harder time at the same rpms. These older hulls are not as efficient as newer ones and i bet your slip is higher than 7%. If your propshaft is deep enough to get that kinda slip, your top speed will likely suffer a bit. I've played with props and spacers so i know. The bottom of your boat is probably closer to our Jags, than say, an Eliminator which is alot more efficient. Hope this helps.

I bet the warlock hull is very close to the Eliminator hulls of the 1990's. It sure looks similar to my 1989 27' and has a center pod unlike our Jags. I agree that 7% slip is pretty optimistic. Doug

I am most interested in all around performance. I want to be able to hit 5600 rpm at what ever altitude I am at because everything I have been taught tells me that this is better for the motors than lugging them. Besides, its seat of the pants performance that counts, not top end - at least in my opinion!

The previous owner thought that 24 pitch props would give me 92 mph.... Once I get a GPS and new props I will find out!

QUOTE=27daytona;3286846]Rick, I have run my Jag from Garwoods to Emerald Bay wide open with the wrong props without any engine damage. I usually run between 5800 and 6000 rpms and had the boat propped wrong and could only make 5000 rpm. I threw a blade and had to use a back up set. The motors just react with the larger pitched props by running with less rpm's and maybe outside of the power curve and the result is less topend and slower acceleration, not engine damage. Try Rob's props and for the money they will be very close. Again, the nice thing about Bravo 1 props is they are cheap and easy to swap or trade. I still have some props for a bravo drive but they they are Mach's 4 blade and Mirage 3 blade, both L and R's that I would sell cheap, but I don't think they would fit your application. Good luck and I sure wish spring would get here. Call me if I can help. 916 539-2540. Doug[/QUOTE]

Doug, you have been a great help. Right now I am just going to wait for a warming trend and then do some work on the boat regarding checking/replacing the impellors and fixing the oil leak on the port drive. I also need to modify the cover because it has seats from Skater in it ( perfectly matched material and color to the rest of the interior too. ). I also need to find a way to do a little work on the bow trailer stringers.

Keep an eye on the weather at Folsom and lets go there when it hits 70 - 75 degrees! You can call me too at: 775 287-8458 cell

My son just went to Vegas and bought a 2003 Crownline 266 with a 496 and triple axle trailer for $14,500.... Its parked in my driveway covered with snow... Nice family boat.

Rick

I agree, my slippage numbers are typically at 15%, but I have been as low as 11% when the conditions are perfect.