Re: Drive heartburn
 

I'm of the opinion that when you "torque load" a drive it tortures the drive AND your motor.It sounds like we have very similar setups,my motor (procharged 540) made 944hp/880ft lbs tq at 5600,907hp/917ft lbs tq at 5200 and tq peaked on most dyno runs around 960 ft lbs at 4600. In my single engine baja 272 v w/std length outdrive i can pull a 30 pitch labbed merc prop to 5800-5900 rpm's,with a non-labbed 32 i lost a couple mph on top and pulled to 5200-5300 and boat acted evil,it wanted to bow steer,motor sounded like it was on a extended dyno pull. It cruised at same speed at 3500 that it normally does at 4000rpm's BUT i was showing 2-3 psi of boost to cruise at 4000rpm's where throttle isn't normally open far enough to show boost w/30 pitch at that rpm.If you lug your motor hard too far below hp peak then it increases your chances of detonation and strains your drive. I ran a 32 labbed this weekend,cruised nice on the midrange,took considerably longer to wind out above 5000 rpm's though but motor could pull it to 5600,I don't know where your hp and tq peaks are but you might want to try a 32 labbed also,Smitty

Re: Drive heartburn
 

I was only playing with props with the 34. The stock 32 buries the bow and I don't get the top end at all, I also have a 30 lab finished to 31 it rocks but I can get 6200 to 6400 with it. I think with a new XR,etc. with 1.36 that is my prop of choice.

Re: Drive heartburn
 

My 30 lab finished to 31 runs 6200 to 6400. My thought is that my next drive selection be a 1.36 and my 31 will be the prop of choice. The 32 buries the bow and I don't get the WOT speed I should be.

Re: Drive heartburn
 

my non-labbed 32 does the same thing on my boat but I tried a labbed 32 this weekend and it felt good like my 30 does except takes a little longer from 5000 up to pull to 5600,Smitty

Re: Drive heartburn
 

Billy has a spare set of non-labbed 30s sitting in his shop. Stop by and see him and give them a try. Just make sure you get a L & R since there are 3.

Re: Drive heartburn
 

Max torque is at 4700 (760 ft. lbs.), max HP was at 5800 but was within 1-2 hp from 5400 -5800 and maxed out at 720 hp.


Thanks, I'll give him a call!

I think a labbed 32 may be the ticket though! :evilb:

Re: Drive heartburn
 

Read the "Tech" artical in this months Powerboat Mag...The one with the Tiger and #6's.
Getting the rpms up will save the drive.
I would go either XR or Teague Platinum...don't waste your time and money on the IMCO's.

Re: Drive heartburn
 

I'm also of the opinion that the IMCO lower case causes the props to "bite" way to much while under way, making re-entry that much harder on the drive. Any thoughts?

Re: Drive heartburn
 

Nobody's "reworked" bravos are going to take flying in and out of the water for very long...I do think there is something to running lower pitched props with LESS blades. I kind of look at it like its a cluth or torque converter. If its "dumped" in the case of a cluth or "locked" in the case of a torque converter there is nothing to help take the load..........The weakest link is going to break. Go to the dragstrip and watch what happens when a redneck spends all of his $$ on the motor, puts on slicks and does nothing to the drive line then launches the car hard.....more often than not something goes BOOM. :p

Re: Drive heartburn
 

The 1:36 lower gears are more money to replace when you do wear them 0ut. And you will. Most are going with the 1:5 unless they run out of prop. Just did a drive and swapped to 1:36 to keep the 32" prop. He added 200hp (966hp to 1150hp) and didnt want to change the prop.. worked out well..
The Velocity I did, was like yours with a blower, he runs 90+ I believe, not sure what prop, but 1:5 gears..
A well setup XR will go a long way for you, driven with respect.

If you would like to discuss setup and options on an XR.. give me a call before 9pm, would love to talk.

Dick
616-335-8446