Bravo XR drive breakage
 

Taking a survey as to what you have personally had happen to your XR drive if it broke.

I need to know what failed first, not the other parts it took out in the process.

I am working on an improved upper gear set and also think the lowers are an issue for some as well.

Thx

The lowers seem to last longer then the uppers by a pretty good margin, you'll twist a prop shaft off before you loose the gears. I think in the upper the case is the problem though, not so much the gear set. Once you get any kind of HP and the case starts to deflect it game over for any gear set.

In mine i scrubbed teeth off the upper gear set on the left hand drive. Also noticed the top cap bolts were finger tight leading me to believe they had stretched and lost tolerance. Didne really take anything else out but the gear.

Broke a tooth off the upper gear set and you know the rest of the story .

On the boats I deal with,,,,, I would say about 3 to 1 uppers to lowers

Your poll is wrong. :lolhit:


Should be:
Broke XR Upper gears 1 time
Broke XR Upper gears 5 times
Broke XR Upper gears more than 10 times

I dont know about you guys, but Merc never should have done away with the TRS drives........ Of course they would have never made millions selling replacement equipment for the bravo drives------ like hooking up twigs to a tractor motor and expecting them to last....




Jim

imo,3 problems with xr uppers,1 the cases flex,gear contact pattern changes and then the teeth break.2,due to the physical size of the gears,it can only handel app 500 hp.3,the quality of material used in the gearsets is horable,no wonder they fail.

when products are driven by marketing rather the engineering thats what ya get . . . . .


I agree would have loved to see a second generation TRS type drive. Simple robust drive with a solid trans for six to eight hundred hp range . . . . or in other words Konrad :D

and this is the issue everyone wants to gloss over. the Bravo was engineered to handle less than 400 hp in a light runabout. its was created so they could put big blocks in runabouts because the Alpha could not handle it. Unfortunatly all the manufacturers wanted them because they dont have a transmission and they could move the back seat back and have a bigger cockpit. because they did that they kept telling Merc to make it handle more power because they already built molds and did not have room for a trans for a TRS or Speedmaster. as a result there is now no step from a crappy Bravo to a #6. it does not matter what you do with gears, the next weak link (and there are a lot at the power everyone wants to run) will show up (gimble, shafts, housing, etc). as Jim said "twigs hooked to a tractor motor".

Only have had 1 of my lower sets go and 1 lower set
on a friends boat...have a pile of uppers tho.

XR gears in an IMCO case , upper gears pitted and started going away . But that's with about 850 HP

Couple of uppers for me
lowers are all good

Upper gear set and top cap - HP525

funny, I had 2 600hp behind trs in a heavy old formula never had a problem

Broken both top and bottom but def. 3 or 4 to 1 top over bottom.

I've replaced several upper gear sets just due to normal wear. I think someone already touched on the fact that it is a marketing item for Merc rather than quality control. No diff than GM installing non-grease able fittings from the factory so you have to replace them.

Does it matter which direction the drive is rotating. I ask this to wonder if the load is on the top cap or the floor of the case.

Funny that back in 1988-1991 era, you had a couple options when choosing power in most offshore boats.
(Black Mercruisers)
454/330HP=Bravo one
454/365HP=Bravo one
502/390HP=Bravo one

(Mercury High Performance)
454/420HP=TRS
502/465HP=TRS

Anything bigger than that you got SSM IIIA, V, and eventually 6. How about the early 525SC hooked to a SSM IIIA? Talk about reliable!!! A drive rated for 750HP couple to a 490HP engine.....its like a XR behind a 454/310HP MPI.

At that time, you could not even get a 454/420HP Merc Hi-perf engine coupled to a Bravo from the factory. So, I would put a TRS/72C up against a Bravo, or bravo XR any day. Now if they had kept the TRS, and made some shorty lowers for them, that would have been cool.

yes it does, the left hand drive pushes up on the top cap under power and, in my case, stretches the bolts allowing the tolerances to go out.

sorry, but this poll is like asking everyone who attends an aa meeting "raise your hands if you like to drink"! we all know that the bravos break and break yet you keep going back to the fountain for another desperate cure. why not start a poll on the alternatives to bravos rather than the next drug for bravo owners? the reason everyone is hooked on these things is that so many mechanics are making their living off repairing them to the extent it would be finical suicide to recommend or have the customers change to anything else.:poopoo:

Only vertical shafts lately....but I've been cheating.

Now if they had kept the TRS, and made some shorty lowers for them, that would have been cool.


I believe merc did experiment with that but they actually built a few prototype 4" shorter uppers for the TRS I know because I still Have 2 of them with speedy type lowers. they will go in a small twin engine Cat with real big HP.

Call it what you want guys , but the fact remains that between the crappy drives and the junk headers and a few other unspecified problems Merc has done less than a satisfactory job of keeping their equipment running the way they were expected to perform by the public ....... Dont think I am ever going to buy another boat and I have been lucky over the years to have what I have had ..... But if I do it will not be a Merc set-up !!!!!!!!!!!!!



Jim

:daz::daz::daz::daz::daz::daz:

Everything at Least Twice!
Ok maybe I have not killed a Lower CASE!
But then again??? I lose count

ditto

i only broke 1 lower, personally i had 250+ hours on it, but i was told it was original and had 472 total.

Boatless--
To address your point- if I converted over to Arnesons or SCX's to eliminate problems,I would be spending 75% or more of the boats total value. You obviously missed the fact that I am headed towards having an option for the 1000's of bravo's out there today. So the way I look at it is with my parts, maybe your drive will last 3-5 times longer or may never break again for a reasonable amount of money.

And if you didn't want to attend the AA meeting, why did you open the door and walk in ????

Imco SC's behind Procharged 500efis
EVERYTHING except the case some parts including upper and lower gears multiple times
Baby the sticks and change fluid 15hrs follow all "bravo driving" advice with no increase in life

chewed up countless lower gears (15+ sets) , sheared off 2 prop shafts and 3 vertical shafts, all billet good stuff. Scalloped one xr soft upper pinion gear in 50 hours but found it on inspection and swapped it out, sheared the floor out of 1 xr upper gear that was mistakenly modified for a bigger bearing which in turned weakened the gear. Currently something is chewed up in my xr somewhere but haven't gotten time yet to pull it off and see since boating season ended. With the max worx tower and all their other stuff I have over 400 hours on my xr gears in my upper at 750-1100 hp, Smitty

How does the xr differ from the bravo 1? I am building a new 600hp motor for my 280 velocity that has a b1 and have heard of guys running 700 hp with stock b1 with out to many problems. Is it due to the 280 being a light boat? I'm still new to this, but was under the impression the xr drive was an upgrade to the b1.

In my industry we have transmission failers when using stock gears behind the high hp bike motors we build. Years ago we started cryoing gear seats and found that to extend the amount of power the gears would hold by about 10-15%. Still in need of stronger gear sets we started having complete billet gear and output shafts made up. The billet seems to be about 50-55% stronger than factory gears. Are there no options like this for boats? Or has it been tried and doesn't work.

For the bolts stretching problem. Why not have arp make up a set of bolts. I'm sure they can make a stronger option. I have an account with them if someone were interested in experimenting with having a bolt made.

I think the bavo shop cryo's gears or use to...check with them

http://www.bravoshop.net/

Teague rebuilt my lower and I got a new Teague Platimun upper, no trouble yet but only have about 10 hours on them. I was told that teague has the gears cryo'd

I don't need it done at this point. It was more of a question if anyone has tried it.

Does no one make a billet set of gears?

The XR case has a steel tower insert to support everything along with all the gear upgrades.

Cryo treating helps extend the life of the gear to gear contact surfaces, but due to the design of the gear, it will fail eventually if too much torque is applied.

Also I don't feel the top caps lifting up has anything to due with the studs themselves. They thread into an aluminum case and will stretch or pull out the threads. I had one pull out. I heli-coiled all 4 and no issues loosening so far after 100 hrs.

When will your solution be available? Straight cut or spiral cut gears? Whats the target price?

I'm going to say something that will probably be torched..but nonetheless...I have always wondered why if you were going beyond 600hp wouldn't you convert to a VI...It seems like that is the next level since SSMIII are gone along with trs drives? I know the cost is prohibitive to a point..but once you've trashed 3-4 drives..wouldn't have been better to go with the VI when you put extra power to the boat...just curious why more people don't make the switch to the 6 drive from the start?

might be useful info if you guys stated the hp in front of the broken xr...i have only 10 hours in front of 600hp...so far,so good

Had the nut fall off the vertical shaft in the lower wrecking about everything in it.

I run mine left handed because the boat lists to the port side with a righty. Sucks, but I have not had a problem yet.

Get those arnesons installed and you will have no worries!