electric504

While I am at it, I need some input. I have a 540 with a Vortech J series supercharger, Bravo 1 that was rebuilt to an XR by Max Machine, and a 30 pitch prop. Mark Boos at Presicion Marine Dyno'd it at 672hp @ 5400 rpm's. I can only get 4800 rpm's (my gauge says 5000 but the computer said 4800) and 75 mph out of the boat right now. Seems to me i should be running faster than that, my friends stock 496 runs over 70. Should I try a 28 pitch and pick up the rpms? I like the way my boat runs and my fuel econemy is great in the midrange but something just doesn't seem right?

Steve Zuckerman

Boost builds with RPM (particulary with centrifugal superchargers), and speed comes with boost and RPM. You probably aren't getting much boost @4800RPM. Try the 28. My boat is as fast or faster with a
28" P5-X as it is with a 32" B1, because I can spin it faster (+400 to 500RPM).
Regards,
Steve

electric504

I have the boost set @ 4 lbs. I am getting 627 hp @ 4800 rpms. I didn't want to increase the boost because I run the boat every Sunday with the family and wanted to keep it somewhat reliable.

Rage

I can concur with the previous comments that the Rage is prone to chine walk approaching 80 trimed out and once you get the hang of it you can generally keep the hull balanced enough to keep it from getting extreme. This is true for relatively consistent water taking waves head on or going away. Cross waves all bets off. I have the IMCO single ram external steering. Some times additional trim out helps stability in this mph range as well.

Rocket Man ran, I believe it was, 107 mph in a Rage on nitros a while back at a west coast shoot out. When I asked, he advised that as long as he was accellerating the handeling was ok but got squirley when shutting down above mid 80's or so. I believe his comments was regarding a straight line run only.

As also mentioned speed reduction should be cautious when in the 80's range and above as well as trim reduction.

Rage

I assume your motor is a 496? If yes do you still have the stock 496cast aluminum pistons in your current set up?

raytart

iTrader: (1)

Here are a few photos
Pics 1 & 2 are the new 26 pitch prop that was labbed (Thinned out blades and diffuser ring cut down) It was cut down to be even with the back of the prop shaft.

Pic 3 is my old prop. Notice the length of the diffuser compared to the 1st two photos.

Like I said earlier... I changed my gear ratio from 1.50 to 1.36 as an expriment in hopes of gaining top end. The orig. setup was spinning a 28 pitch bravo to approx. 5300. With the 1.36 gears I couldn't spin that prop. So... I got a stock 26 which I could only get to about 4500 rpm. The speed was almost the same as the orig set-up but the boat was chine walking bad especially when coming off a full speed run. I had TSPM send the prop to his prop guy and he thinned the blades to pick up rpm and cut the diffusser to help the handling issues. Not sure why he thought it would work but I agreed to let him do it. Well IT WORKED PRETTY DAMN GOOD. I still need about 200-300 rpm so I'll be sending it back. I also took the drive spacer out prior to labbing the prop in hopes of that helping the chine walking but it made no differance so I put it back in because I had positive results with it when I first installed it. Am I making sense???


And Yes - it's a B1 4 Blade!

Nordicflame

iTrader: (4)

With the IMCO exhaust and ASM recal I would guess NOT a 496

Rage

raytart,

I am really interested in this chine walking versus prop mods you experienced. I hope you do not mind a few more questions.

Did you experience the same chine walking with the stock 28P B1 and 1.50 gears that I believe you said produced the same mph?

Since the chine walking with the 26P B1 and the 1.36 gears went away when you had it both labbed and the diffuser ring removed how do you know that the labbing alone could not have been the reason that the chine walking was eliminated?

Did the prop shop mention fixing any other chine walking problems by diffuser ring removal only or other experiences that lead then to the conclusion that diffuser ring removal is the key to eliminated chine walking.

Do you have the number for this prop shop?

raytart

iTrader: (1)

Hey Rage

Not a problem answering your questions.

The answer to your first question is NO. No problems prior to gear change.

As far as the labbing of the prop eliminating the chine walking... I really can't give an answer on that because the labbing and the cutting the diffuser were done at the same time. I never spoke directly to the prop guy. I spoke with my dealer (TSPM) and he relayed the message to me. But I recall the conversation and the prop guy told him that cutting the diffuser would help with the handling issues. I'm not even sure of the prop shop or the guys name. Have you asked this question under prop forum? I read some of the posts and there seems to be alot of knowledge there. You may find someone who has done this before and possibly get a more informed answer. Keep in mind that with the gear change, the prop shaft is actually spinning faster but the motor is not. I tried other props with the new gear change and did not experience chine walk. But those props, all of which were B1 4 blades did not allow me to get even close to max rpm.

Like I said in an earlier post "Are you willing to expriment...$$$. I was and I'm still experimenting. I still need a few hundred more rpm's and I hope to get over 80 mph. If I don't get over 80, All of this is one for the books. But I must say that I did loose "Punch" But not too bad. I do like the way the boat carries itself now. It feels like it's riding higher out of the water and the sensation of flying reminds me of driving my old Hydrostream.

Ray

Rage

Thanks raytart. I will check and see what the prop forum has to say.