switching from XR to HT B-max
 

Has any one done this? Is there a lot of work to change over? Any suggestions or hints would help. Thanks

I went from a Bravo to a HT B-Max no nonsense at all direct bolt on. I only wish there were more selection in gear ratio. I would do it agian in a heartbeat. It seams to be bullit proof
My $.02

Havnt done it but I see your going to be putting them on a 36ft cat. My buddy had them on a 37 talon and in two years blew up around 5 or 6. We switched to number sixes and no more problems. It also seems Bmax's slow the boat down quite a bit compared to a regular Bravo. The drive should just bolt on though.

I had some help but it was pretty much bolt on.

Brian, what did you put it on?
Did it slow you down much?
Did you use the bravo gimble?

We have them on our 382 Fastech that is for sale now. It was pretty much just a bolt on. It did slow the boat down abit. However, the plus side is we have not broken since. I should add we are running supercharged 572's.

I bolted mine to the stock gimble. I lost a couple of MPH but it isn't breaking and it's behind about 750 hp procharged 454

Thanks.
How much heaver do you think it is than the bravo?
Does it seem to shift the same?
Did you reprop and what gear did you go with?

sorry about all the questions:angry-smiley-038:

I don't know how much heavier it is but if I recall it is about 180lbs. It shifted very hard at first but shifts normally with hours. I have the 1:30 and had a 1:50 bravo I went from a 32 to a 24 Bravo 83.6 GPS. I'm rebuilding the engine now freshining and adding a couple (it is apart) we'll see next season.

I'm under the impression that B-max only sells there drive with merc 1.36 lower gears or the other steep lower gears because the 1.36 gears have poven to be slightly more durable. I do know they are using merc lower gears,not some extra strong aftermarket version or anything. Has anyone tried re-gearing the drive with merc 15/19 1.50 lower gears? By cryoing then giving the lower gears a multi-step surface treatment that ends with them having a very smooth finish I have gotten the 15/19 1.50 gears to last much longer then they ever did in stock form on my boat with a bravo drive. My understanding is that most boats go slower when switching to a B-max because of the extra friction of the larger upper gears and bearings but what I'm wodering is if some guys are losing speed from the overall gearing and re-propping why not try going back to 15/19 lower gears once the warranty is up,Smitty

I thought the "new" HT series had a better lower than the original or it was different. If it is a merc lower gear why wouldn't Dean use the
gear to give it the 1.5 ratio (let me guess, not as strong ,as you stated)
I thought I heard the Imco lowers bolt on to the Bmax with a slight water jacket mod.
Does the Imco lower use merc gears?

Has anyone tried these on a larger cat? Im putting on a 36 Spectre with apprx 800hp...keeping my fingers crossed on more reliability.

The Imco sc uses stock merc lower gears,the new 35,000$ Imco 1000 uses something extra hd/special. As far as the B-max, I am not a expert but the second hand info I have is that the "HT" still uses merc lower gears but has been re-fined in other ways,Smitty

i have done the install a few times. it is a bolt on, simple install. in all cases they slowed the boat down between 2.5 and 6 mph. a-the gear drag is greater and b- the foot print and dynamics are off.
the biggest draw back is sue to the xtra weight of the drive itself and the fact that you now move the weak link from drive to gimbal. on 1 boat the drives no longer blew , he ended up breaking two gimbals . which tore up the transom, props, rams, and almost killed everyone in the boat.

My thoughts were a new Imco gimble (I've heard it's much stronger than the merc HD)
Then throwing on the HT-Bmax

i would strongly suggest that as well as the helmut they offer

Smtty,
I totally agree the majority of my speed loss is a result of the gearing and not so much the weight.
Maybe after the warranty I may.
Bob

If I recall that thread there was alot more to that story.

of course. but from a mechanical or engineering standpoint the weak link is moved and that is fact. same issues on a high powered single engine, busted gimbal.

not blaming or trying to disuade anyone from b-max, just offering info. in my findings the stronger gears, heavier weight hanging from a pivotal point not enginered for, and larger surface area, there is an effect to the overall performance of the vessel and its attributes.

As I understand it Dean offeres a gimble assmy for his drives. I believe it requires mods to the transom. Is this correct?
I'm looking for options as well and I would prefer to go with a gimble and helmet assy that is a merc cut out in case the boat is changed back to bravo stuff.

Monstaaa, Do you believe the Imco complete transom assmy w/ helmet, gimble, and trim rams is up to the challenge?

Sorry for jumping in the middle of this Bonecrusher

Monstaa,
I would agree that the weak link does move. That said I have not seen any additional stress in my application. In the threads discussed I believe that an impact with a foreign object had something to do with it. Any upgrade to a weak link is suggested and should be a part of your budget when considering any project. Just as I learned with my modified procharger project. A Bravo is a disposadrive in that application I don't care who is driving it is just a matter of time you'll break it.

no impact. just high side load. off a big wake, landed to the side and bang, broken gimbal.
their is truly a reason why items are designed as a match pair. from an engineering stand point. a similiar analogy would be to analize , from a stress standpoint , the effects of using the "stern jack" on the transom assembly as a whole. big long studs into the helmu with a bilet piece of staock 6-8 inches long. not good.
as for the bravos i feel they are only as good as thier operator.

as for the bravos i feel they are only as good as thier operator.

When you press over 600 HP thay just can't take it. I have had them grenade on glass flat water while decelerating. Some make them work but I don't think they drive them hard.
I don't know enough of the gimble situation to give an opinion I did not see the parts, etc. I've been OK so far.

the unfortunare thing is that too many people "rebuild" bravos. once they grenade their petty much junk. guys rebuild them, using the same casing that has been stretched from the previous explosion.this is most of the cause ofmajor failure after initial blow up.
i have set up at least a dozen boats between 35 and 42 with bravos and 750 h.p with out reoccuring failures. and they are here on long island where you have both flat water in the large bays as well as some of the roughest inlets known.
it reall is my feeling that used properly and with proper maintanance they will live with 700+ without problem.

When installing a b-max drive would really consider an imco hd gimbal,especially on a cat,lots of side load with the high speeds.The b-max is heavier than the standard drive about the same weight as the bravo3(according to dean at bravo shop)the difference is bravo3 boats are lucky to do 65mph not 130mph,breaking gimbals at speed is bad news!!

Could you guys post some pics of the B-max's on your boat.
I would like to see some other setups.
Here's what we did.

Question for Monstaaa, when it comes to a bravo drive life, do you think the oil cooler system from Drew Marine would help?

I think it would help alot in my situation. With a drive temp gage installed I found that I could get the oil in the drive VERY hot, when running hard. If the Drew Marine system keeps the oil temp low all the time, then it 'should ' help with gear and seal life right?

Also, about the B Max, I looked into them last summer when my bravo failed. I found a few draw backs with the B Max. I couldn't run my exhaust through the drive, I would have to buy mufflers. Also with external hydraulic steering, without modification, the steering angle is reduced. This wouldn't help when docking.

Both are liveable issues, but just wanted to add to this thread.

Smitty, from what I understand they couldn't get the 1.50's to hold up for any length of time and that it had something to do with harmonics or something like that. I think the upper gears in the BMax change the gear ratios slightly... It was explained to me in detail about 3 years ago but I don't remember exactly what it was.

I lost 2 mph when I made my switch... I blew two brand new IMCO Extreme SC's (800 hp rated in a 10k boat :rolleyes:) in about 20 hours on 715 HP.... Thus far I ran 100 hrs on the BMax with 715 hp the first year and 830 hp the second year..all ocean running.

I had one small issue with the coupler that connects the verticle shaft in the lower to the upper but I've had ZERO downtime since I bought these drives well over two seasons now.

With that being said....100 hrs on them I sent them back to Dean to be fresheshened so I can go another 100+ hours without batting an eye! :cool-smiley-011:

Thats awesome, I hope I have similar success!

that kit actuall does drop oil temps most effectively compared to typical drive shower's. and along with a good synthetic gear oil like mobil 1's there would be a significant term life expectancy.

Doesn't the Bmax have water cooling passages ?

Yes.

Yes, the whole case is encapsulated like a manifold almost and exits thru the top cap. :cool:

I didn't know it exited throught the top cap! Does the drive not supply to the engine?? Or does it do both?

Both...

There is the regular pickup that supplies the engine, then there is another pickup just above the bullet which supplies the water to the drive. The water exits via two holes in the upper cap.

Dont Do It...aside The Gimbal Has A Tough Time Holding Up On A Cat To Begin With W/o The Extra Weight Of A Bmax.. The Drives Just Dont Hold Up And The Service Is A Joke !!!!!.we Pulled 5 Nor-techs From 1 Poker Run With 11 Broken B-maxs..... Last Year We Had A Customer Without Going Into Details Had Terrible Luck With The Drives And Servce.... Just My Input . You Asked For It .. Good Luck Either Way.. Oh Yeah The 36 Diesel Spectre We Have Went Through A Dozen Of Them Till Finally The Lower Unit Flat Fell Off.. They Complained About To Much Torque.. We Fixed The Boat By Putting Stock Xr Drives On It And Never I Mean Never Had A Issue AGAIN...

:food-smiley-007:

:grinser010:

not good news. You pulled 5 boats w/ 11 broken drives? was one a triple?
With hard core comments like that some details would be nice.
And you went through 12 drives w/ one boat alone?
What kind of power were you running ?
Did you have any gimble failures? And what gimbles were you using?
And what kind of pwr were the NorTechs running?
Is it true that the bmax is rated for 900 and the XR is around 550?