2001 bravo 3 recurring oil leak

I have a 2001 Osprey 30 with a Yanmar 6LP-STZE mated to a Mercruiser Bravo 3 diesel drive. Have owned the boat since it was new. The last 3 seasons I've had a recurring problem with the seal in the top of the drive failing, allowing gear oil to leak into the bilge.
This season-had a new seal installed when drive was pulled for the winter, had oil leak in
July. Pulled drive replaced seal & used for rest of season. Now seal is evidently leaking
again as resevoir is down & oil in bilge. Pulling drive off Monday but I'm sure that it's the
upper seal yet again. Anyone have any idea as to why this keeps recurring? Thanks in
advance for any help.

Re: bravo 3 recurring oil leak

poor seals, rough/rusted seal area on the input shaft

Re: bravo 3 recurring oil leak

Ayuh,... Has the input shaft been changed when the seal was replaced,..??

My guess is, it Needs it...

Re: bravo 3 recurring oil leak

The input shaft was changed when the original seal failed, two seasons ago. There are no signs of wear or corrosion on the new shaft. When the seal was changed in July, upon
inspecting the leaking seal, it failed where the rubber joins the metal perimeter of the seal.
There was no scoring on the shaft & no tears in the seal where it meets the shaft.
When the drive comes off tomorrow I'll be able to see where the present seal has failed.
Thanks for the responses guys.

Re: bravo 3 recurring oil leak

If the seal leaks NOT at the lip where they normally do and it is where the seal meets the metal perimeter, My suspision would be whom ever is doing the repair is not installing the seal correctly.

The seal is contained in a aluminium outer ring "carrier"aluminium "assembly". The "carrier" can be purchased with the seal allready installed or just the seal itself can be purchased and the aluminium "carrier" reused.
If the shop is reusing the aluminium carrier they may not be using the correct seal installation tool/method....or maybe the seal is bieng installed backwards....

Re: bravo 3 recurring oil leak

Kghost, Thanks for the response.

I'm not a mechanic, but to me it appeared that the seal had been istalled correctly.
The seal has a metal perimeter that is pressed into the drive housing (as the mechanic
had showed me). It was the inside edge of the metal where it joins the flexible rubber
portion that the seal separated allowing the drive oil to leak back into the bilge.
As I said before, when the drive comes off tomorrow we'll be able to see where the
present seal failed. But this will be the fourth time in the past 2 seasons where this
seal has had to be replaced, with around 130 hours running time total.

I seem to recall reading somewhere about using synthetic drive lube & a "drive
shower" to lower the operating temperature of the drive. Does this ring any bells
with anyone?

Re: bravo 3 recurring oil leak

I use nothing but merc highperformance gear oil, IT IS synthetic......

As far as temp goes if you are running a desiel I would imagine you rarely go over 4000 rpms, most likely 2000-3000. I doubt it would over heat. I "think" hi temp outdrive upper gear cases run hot when run above 4000 rpms for sustained periods. I could be wrong on this point but is would seem to make sense to me.

For your info.

The upper carrier assembly, ( yoke, double bearings, spacers, seal,gear and lock nut, o-ring) and large outer nut to hold the entire assembly in, is the jist of the parts.

The seal I believe you are refering to is pressed into a aluminium outer ring and only HELD in place when assembled. This "upper carrier" seal as I call it, and I have replaced many, that and the large oring are the only two items that keep the oil in the outdrive. If they leak it will allow gear oil to leak into the bellows. Once in the bellows it will leak into the bildge thru the gimbal bearing.

Re: bravo 3 recurring oil leak

The Yanmar is a high revving diesel, I usually cruise around 3,400 rpm. Yes, the seal as you describe it is the one that is failing. As the mechanic and
anyone else that I've asked cannot give me an answer as to why the same seal keeps failing, I'm looking for any possible reason as to why. The down
time has been killing me & obviously it's in the back of my mind-when is it going to happen again.

Thanks again for taking the time to respond.

Re: bravo 3 recurring oil leak

Is he using genuine Merc parts???

If he is using a seara or other that could be why.

Also if the seal lips are not sealing maybe the yoke outside diameter is incorrect. you would need another to measure to check. It could happen. Also just some bad seals, it could happen also.

I have never had a mis fitting one but I have had brand new ones with lip issues and failed before use while doing a pressure check after assembly.

Again if he is using the incorrect seal driver if replacing only the seal that could also be why.

report back after dissassembly and take a few pics and post so we can see....

Re: bravo 3 recurring oil leak

Okay I'll be sure to report back, hopefully drive will come off tomorrow.

I'd asked him previously, he assured me the parts were genuine Mercruiser.

After reassembly the drive has held pressure, told me that as well, SOP to check afterwards. It's been after using boat a few times that problem recurs.

I'll ask him about the seal driver.

In your experience, have you seen excess heat make these seals fail? Perhaps I'm on a wild goose chase but I'm searching for any solution at this point.

Thanks again.

Re: bravo 3 recurring oil leak

If it`s a CR manufacture, merc did have lots of trouble years ago with the seperation you mention. Try cross matching to National. The one for Alpha`s is National 712250 ,it may be the same size as Bravo.

Re: bravo 3 recurring oil leak

hardwired said:

As the mechanic and anyone else that I've asked cannot give me an answer as to why the same seal keeps failing, I'm looking for any possible reason as to why.

Click to expand...

What is your drive serial number please?I have a feeling the answer to this question is going to be at the bottom of page 3A-44 of service manual number #28 (part number 90-8631601). You might want to have your tech take a look inside service manual #28 to see if this fits your situation that your having.The manual shows for the (Bravo X AND the Diesel Drive) the oil seal being installed on the yoke shaft first before the retainer nut, Where the standard drive & the XZ & XR drives show the oil seal after the retainer nut, So if I'm looking at this right then that might be a possibility, But I'm not 100 percent sure of this myself, But I would call Mercruiser to confirm this theory though. Also FYI, if I did my home work correctly without having your drive serial number available at this time, you or your tech should be using service manual number 28 ? Since it covers years 2000-2005. Hope this helps you out some, Good luck with it.P.S If you find this information out to be true or not, Please let us know about it for future reference, Thanks. By the way sorry about my posts wording running all together as one like this, For some reason the forums computer system is doing it automatically to all my post now.

The drive was removed but the mechanic hasn't disaasembled the top half yet. He is off for a few days. As soon as I have any more info I'll post it. Thanks to all you guys for your help.

I have the same issue and I'm at a loss as to what to do short of buying new drives. I have twin 350 mags with bravo 3 drives. Starboard side drive started leaking from top seal 3 summers ago. Had my mechanic replace the yoke and seal and also had him do the same on the port side as preventative maintenance even though it wasn't leaking. 3 seasons later, both are still leaking from the top seal after 4 new seals on each side. Last time, he had me change the double bearing as well.Has anyone solved this one yet? Seals are fine for 10-15 hours then they leak.I should have left the port side alone ;-(Mike

Anyone?

Do your drives have lube oil monitors?

Yes I do

I was thinking that if there were no monitors it might be possible that the drives are overpressuring the seals (due to heating in use) and causing premature leakage.
But with monitors that should not happen because any over pressurization will usually back the fluid up into the monitors a little.
There are lots of Bravo 3 drives out there and I find it difficult to imagine that there is a recurring seal failure issue.
I would get hold of Merc technical services and describe the problem to them and see what they have to say.
Changing seals every 10-15 hours is kind of crazy.

One good thing about having the monitors is that the drives will always have positive internal oil pressure relative to the outside water, and this should prevent water intrusion into the drives. But still, leaky seals are a nuisance.

Rod