DonRoc

This is my personal boat. I wanted something tech, and fast. My goal is 115 mph... The boat a 2005, 29 Kryptonite.
I finally made up my mind, on the major components for my Kryptonite motor build. I was struggling between a smaller CI motor and some RPM's and a Large motor and not so many RPM's the issue was in which size prop I could use. I didn't want to go to 1.25 gears and didn't want to swing a monster prop on a single engine smaller boat. I wanted the boat to have more of an influence of where we were going than the prop..

So I decided to settle in the middle and order a Merlin III tall deck. It will be a 572ci with a 4.375 stroke and 4.560 bore. I will set it up to spin between 6000-6200. That gives me a few hundred RPM's of safety margin.

Some of the things I have firmly decided on 572, AFR 357 heads, M-5 Procharger, Accel DFI. I am ordering the Block and heads Monday or Tuesday. Procharger is having a good sale starting Dec 15th so I am waiting for then to order the blower. Once the motor is built I am going to have Performance Marine (Saris Racing) set it up on the Dyno, and fine tune the DFI on the water after that.

GPM

You might want to consider a 4.5 crank and the Fast Ecu,
more torque and easier to tune.

Sunshadow

Do you have any parts yet? I have a brand new 572 rotating assembly 4.5 bore and 4.5 stroke MerlinIII. project got put on hold I'd make you a good deal on. It was built by Andy Costello here locally same guy who does GLH's engines for the DBI boat. http://www.offshoreonly.com/forums/g...rking-mti.html

DonRoc

Maybe some more Tq with the longer stroke but less RPM's. I want to turn a little smaller prop, so I need the RPM's. to make my goal. And I really dont need any more torque. Remember its a 29', that really is a 27' with a platform. With the motor it is about 4,000#.

DonRoc

I have some parts on order. I am going with the 4.375 stroke and 4.560 bore.
It is important for me to build the motor myself. but thanks for the offer.

Sunshadow

Cool, post your progress with pics. We'll watch.

GPM

That's about the same weight as my 26, I tried the 4.25, 4.375, 4.5 and 4.625 cranks. 548, 583, 598, and 615 cid.
All Procharged, the 548 and 583 were lazy compared to the 598 and 615. I run the 598 @ 7500 when I go to the shootouts.
Best of luck to you.

DonRoc

4.5 Stroke @ 7500 RPM's? That puts the piston speed @ 5625 fpm.That's a little to fast for me, I want to make it to the end of the lake. Maybe I am too conservative but in my business I cant afford to be breaking down, it would not look good..Maybe if I had a drag boat and was going to be at max RPM's for just a few seconds maybe, but for extended periods of time that is just way to fast. I feel a safe piston speed number is 4500 fpm (that's just me). NASCAR engines @ 10,000 have a piston speed of 5417 fpm, and F1 spinning @ 20,000 have a piston speed of 5219 fpm. So you need to be putting some pretty hi tech custom parts in that 598 with the 4.5 stroke to run 7500 RPM's. I cant even imagine what a motor like that would cost to hold up at those speeds for very long. Maybe I am wrong I never tried it outside of a drag motor in a car that was being pulled down every few runs. Could you actually hold it over even 7000 for long? Maybe some other engine builders could chime in here. I am interested to know what others feel a safe piston speed is....

DonRoc

What Procharger did you use, and how much boost were you using on pump gas? I am going to set mine up on the dyno, but just wondering. Did you dyno any of the motors?

DonRoc

Thanks, I wil post some picks when I get all my stuff.