Mercruiser bravo 3 catastrophic drive failure merc defect

Greetings,

Isn't this boating $tuff FUN!

I have a 2008 Formula 37 PC equipped with Bravo 3 X drives. After about 8-years and about 330 hours of use, the port side outdrive failed.

WHY?

The rear lower carrier bearing unscrewed and backed out of the aluminium drive housing.
This is a left had thread, in a right hand turning prop. It holds the prop shafts inside the housing.

So the carrier unscrewed itself from the outdrive housing, with the prop grinding the aluminum from the carrier, backing everything away from the prop seals. The gap left is not a small leak, but a major gaping area left for the oil to escape.

These drive have been well cared for with annual oil changes, and pulled for maintenance as well.

The Low Drive Oil Warning went off, and we immediately stopped the boat. The drive bottle was empty, and we refilled it. After 2-3 more miles, the alarm went off again, so we shut down the motor and went home on one.

Regardless of how fast you could refill the drive container, it could not keep up with the huge gaping area it left for the oil to escape.

Since the oil went out so fast, and all of it, the top gear set was ruined along with the lower end issues.

I have put a new Outdrive on now $$$$$. However this drive has now cost me nearly $30.00 for every hour of operation.

Talked to Merc, and they have never heard of it before, while my marine technician sees it often and diagnosed what was wrong just by looking at it for about 20 seconds.

Anyone el$e having i$$ues like thi$?

Never seen or heard of this failure. Kind of wonder whay nothing ever showed up with yearly inspections. Its hard to garb hold of that it turned that many times to come off in one season. There should have been some kind of sings in earlier years. Were you doing all the work or was your mechanic. Not throwing rocks at your mechanic just personal inspections are far more detailed then someone being paid by the job.

You can pick up a B3 lower for under 3K with warranty. Complete new cost under 7.5K

All Dodge,

While you may have never heard of this failure, my Mercruiser Technician has seen 3 of these in the last 2 years all on Bravo III's, not happening on Bravo I.

The day I took mine in for the drive repair there were 3 other Formula PC's that were in need of major drive repair, and none, including mine had anything to do with hitting anything.

Each year the Formula Merc Tech removes the out drive, checks alignment, changes gear lube, lubes shaft, pulls inspection plates, pressure checks the out drive, pulls the props and greases the shaft. The last time this was done was 10 1/2 months ago.

Problem with this and the Bravo III's is there is no locking mechanism other than torque to hold it in place. That is true for both carrier bearings in the lower units. Bravo I's have a bend over tab that locks those parts in place, missing from Bravo III's.

As for catching this earlier, besides all being inspected 10 1/2 months ago, the prop shaft RPM is about 2,400 RPM at 3,400 engine RPM. When anything starts letting loose at those RPM's in an out drive, it doesn't take long for things to go south.

I just don't think Mercury Mercruiser does not make an out drive robust enough such as the big heavy 34/37 PC's and 370/400 SS's. Even with the X and XR drives. Its not a horsepower thing, it's a weight issue.
You boat, with your 502 has a great power to weight ratio, get to something like my 37PC, and its a BOAT LOAD of weight.

There is a builder of drive robust enough for these boats, to bad Merc can't get to their level of performance and reliability. We sure know they are already there on Price $$.

http://www.konradmarine.com/

I understand the issue, and I spend most my time on iboats and some other on offshore only. I'll take your issue to those sites and see what they say. There are several folks in the business of repair and building power. Konrad appears to be a heavy built upper with a standard B3 style. This is similar to what Merc has.

The upper Bravo can be had with standard, X and XR, the designation is only on the upper section. Any of the Bravo uppers can have the B1, B2 or B3 lower attached to them. I just rebuilt my boat and motor then installed a Bravo XR upper with new B3 lower. My cruiser is around the 11K mark for a single, your 37 should be in the 18,400 range (9200 per).

Agree the B3 carrier is torqued to 200 ft lb and no Loctite or other sealant other then thread lube (Have rebuilt drive).

One of the worst problems with the B3 is the seals, my new drive came in leaking lube before first use. Not trying to reduce what happened to your drive did not happen exactly as you said, I'm just puzzled why I haven't heard about it before, that's all. Well keep this thread link and post back what I find out.

Mis spoke the inner bearing retainer nut is 200 ft lb, the outer bearing carrier is 150 ft lb. Ya know the bearing carrier is tightened counter clockwise, the prop that has the most friction to the carrier bearing also rotates counter clockwise when going forward.

Check prices from Marine Power Services in Farmingdale, NJ. Even with shipping you will probably save money.

Well posted on both iboats and OSO, there has been no response from OSO and some comments from iboats. Those that did respond don't see how it could happen and know of no other time they heard of it happening. I'm under the impression it may have been a defect in the carrier bearing or threads in housing. To help clarify if pics from other angles to the housing and carrier, should help.

Found out today that Konrad marine builds drives which require transmissions to feed the drive. They don't have cone clutches to change directions.

Real Failure....Bravo3 400SS Pacific Ocean 525's

Different kind of failure, and my first guess is it ran out of lube, or water mixed with lube

18,000 lbs, no prop slip, Pacific ocean swells, 525 hp. ka blam..

I concur with OP's conclusion that these drives are simply not up to the job on these heavy boats. After settling on a 2003 37PC with ~460 hours, I had pretty much resigned myself to replacing drives in short to medium term even before survey and sea-trial, full drive service history notwithstanding. This was based on hearing a lot of horror stories regarding heavy cruisers, spending time analyzing the guts of a BIII and personal experience with BIIIs on a much lighter Sea Ray 340. As it turned out, sea-trial uncovered a really nasty bearing growl in one drive and the other was on the way. I didn't think twice about replacing both drives as part of the deal and just be done with it versus death by a thousand cuts. As far as I am concerned, 300 hours with the combination of weight and primitive Merc engineering is about right - anything beyond that is gravy to be grateful for. I have already started budgeting for next time around as I put on ~100 hours/season. It does tick me off but at least I knew what I was getting into - I do feel bad for buyers that go into it blind or those that have I/Os but don't really need or use the benefits of them.

This is certainly a very interesting discussion with everything focusing on the Mercruiser I/O. How about the Volvo equivalent? Are those more robust?

Don't see VP being any better for the standard DP drive

Many of the higher HP motors turning a B3 drives do fine, but must be driven a bit more easy. Don't drop the hammer, and when running in high swells, if the prop grabs some air for even an instant can blow the drive apart. This is the reason that performance offshore boats have one person designated to handle the throttles. Sure you won't hardly see a heavy cruiser gab air, but all it needs is to lean to one side and ventilate the prop once.

My 10K single engine 520HP cruiser has an XR upper and B3 lower. Lube gets changed every year, drive comes off and checks are done. While my upper is an XR, the lower is the standard B3 as all others. no one makes a twin prop in a high torque model.

If you want a beefier drive but it won't be a B3, need to go with B1XR, or B-Max.

Single prop outdrives on a 400ss are not ideal. I ran one on a sea trial. It took forever to get it on plane. It blew out on a sharp turn. Ugh. The DP-h drive is significantly more robust than the b3. All the gears are larger and helical cut like the old xz. B3 in the 400 does well in lakes and rivers

Greetings,

Could you please send this to Merc, as they are the ones that did not do this right.

Thanks

AllDodge said:

Mis spoke the inner bearing retainer nut is 200 ft lb, the outer bearing carrier is 150 ft lb. Ya know the bearing carrier is tightened counter clockwise, the prop that has the most friction to the carrier bearing also rotates counter clockwise when going forward.

Click to expand...

BeechBoy said:

Greetings,

Could you please send this to Merc, as they are the ones that did not do this right.

Thanks

Click to expand...

These are Merc manuals, so I don't see me sending it to Merc, think they would laugh about it. Not putting you down, just don't see how Mercury Marine would listen to an outsider (non-dealer type)

Send Mercury a page out of the Mercruiser manual? . . . I'm sure that will take care of everything . . .

BeechBoy - Since this thread is 2 years old, I assume that you had to get a new outdrive?