Drive heartburn
 

I've been running a modified 454 Mag with Pro Charger, I have taken out another Bravo drive. Any thoughts on XR, Imco, or others?

Re: Drive heartburn
 

xr great drive imco a step up!!!!! same gears heavier housing :evilb:

Re: Drive heartburn
 

What size/weight boat?

I'm running the same set up. Pulled the motor and installed it in a heavier boat and blew an XZ.

I then purchased a new XR from BAM. Just changed the drive oil after 20 hours. Not a spec of metal. Seems to be the ticket.

Re: Drive heartburn
 

1998 Velocity 260 same as 280 today 26' hull about 4400# runs mis to upper 80's depending on prop gps havn't totally dialed it in yet.

Re: Drive heartburn
 

How big is the boat, weight, and what prop and gear ratio? How much power does it make. I put a Bam XR upper on rebuilt lower, 28' Checkmate, 650 hp. He has a couple of weekends on it. Another one is on a 260 Velocity, with blower motor 750-800 hp.. several weekends on a rebuilt XR. Both were at Hardy pond this weekend and I did see the Velocity run it real hard. Another is 25' (24'?) H2x Baja. 966hp procharged. XR upper, new design with Imco shortie.. 70hrs and upper gears were done, but did not hurt anything. But they tell me he ran it like he hated the drive.. Now it is running 1150hp and 1050ft/lbs and it went 109mph at LOTO . We'll see how long it runs. A properly setup XR will live for a while if driven with respect.
I hope that helps.
Dick

Re: Drive heartburn
 

Blew two IMCO Extreme SC's this year. First one at 20 hrs, second at 30 hrs. :mad:

Giving someone else a shot and having the latest blown drive rebuilt with Max Machine internals. We'll see what happens. :(

Re: Drive heartburn
 

cool panther please let me know how you make out or if I can help out in any way!!!

Re: Drive heartburn
 

It's a 1998 260 Velocity 26' same as the 280 or VR1 about 4400#'s questimations are about 800h.p.
1.50 gears has run a Bravo 34 lab finished to 35 at 4900, running a stock 32 bravo that needs some massaging to get it right.

Re: Drive heartburn
 

Max machine worx gets my vote. I just broke a drive 1 week ago,lower gears started chipping teeth away,ruined most the bearings thru out drive,60 hours on drive since it was freshened-(30hours w/750hp-30 hours w/950 hp). The upper xr gears still looked good,no broken or twisted shafts this time. Drive breakage is going to happen at 800 plus hp if your running any kind of bravo derivative,its just getting it to last a reasonable amount of time. Is there a reason your running a 34/35 pitch prop at only 4900rpm's?If you torque load the drive hard down low like that it will break quicker.If your any where near Michigan mr gadgets can build you a good drive using max parts or any combination of parts you want. I was at hardy pond this weekend, both races I got in were against velocitys like yours,1 had a mph on me ,the other walked away,pretty fast hulls :eek: ,Smitty

Re: Drive heartburn
 

Hmmm, I'm turning a 32 Bravo 1 to 5000 rpm with a full load of fuel and 5300 with 1/4 - 1/2 tank of fuel.

I wonder if a 30" pitch would be better at 5300 full tank and 5600 1/2 tank?

The Valvetrain is set up to run 5200 - 5600, we spun them to 5800 on the dyno. I'd loose cruise speed but if the drive lasts longer than so be it.

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