Bravo 3 Advice Needed

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Denny

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We own a Cobalt 220 (22' Open bow) with a Mag 350 motor and a Mercruiser Bravo 3 sterndrive. The Bravo 3 is losing gear oil at a rate of about half a quart every 5 hours. We can find no external leaks and there is no gear oil in the bilge. I assume the problem is a failed prop shaft seal or other internal seal. I have learned that Bravo 3 drives require special tools so not all shops are equipped to deal with them. Does anyone know of a shop in Page that is capable of diagnosing my problem and fixing it? If you wish to contact me directly I can be reached at dennydmorrison@gmail.com. I appreciate any advice I can get.
 

Jimbo

Well-Known Member
My theory is that the B3 drives heat up in a normal fashion and the oil squeaks by the seals during operation while under pressure.
If you look at the fill cap on the reservoir you will see a small hole that will allow air in but not out. Basically a check valve.
Some have had the reservoir rupture because of the pressure making a big mess. You might try loosening the cap and see if it still leaks oil. It worked for me. B3's run hot on a long cruise while the drive is pretty much out of the water. Hence the drive showers that are available for them.
Some special tools if breaking down the drive but any Mercury shop should be equipped. There are a lot of B3 drives out there.
 

Ryan

Well-Known Member
The oil has to be going somewhere. Either into the bilge (often time a faulty cap or small crack in the reservoir), or out through the seals in the outdrive.

If it is going out the outdrive, I am pretty sure it would likely be leaking all the time - you should see it on the ground under the drive, or at the very least, be able to see some residue on the drive itself.

I should also ask, is this a new problem, or ongoing? Also, do you know how the fluid was changed at the last maintenance? The proper way is to drain out, then pump in from the bottom drain hole. If someone drained, then filled directly into the fluid reservoir, there will be air bubbles in the drive that will slowly work their way up. When I had my Merc, I always filled from bottom to top, and still would have to top off the reservoir after a couple of trips. Once topped off one time, it was good for the rest of the season (around 70 hours).

As Jimbo stated, I would also assume that any Merc certified mechanic (which seems to be everyone) should have the necessary tools to work on a B3.
 

Kidfree

Member
How old is your boat? Has the drive been pulled and gimbal seals replaced? When was the oil last changed, one thing to watch for is seal on drain and fill plugs. I would pull the props and look for oil around prop shafts and exhaust. Leave the lower unit down without the props on and watch over several day (with revisor at full line).
Make sure you are running a drive shower, I run a simreck on my Bravo 1. These big drives run hot I have noticed mine does not build up the white scale with the drive shower on it.....
 

Skibum

Well-Known Member
+1 on the drive shower. We have a B III on a 270DA that has gone to zero mtce other than annual pull, align & grease since we put it 5+ years ago. The mechanic in Page we've used is Bill at B & T Marine. He knows the drives. Also that drive requires the Mercury "high performance" gear lube.
 

Denny

New Member
To close the loop on this post, at least for now: All of the boat repair places in Page are busy with emergency repairs or regular customers and could not promise a solution until fall. All agreed that it is likely an internal seal that has failed. After a little searching I took it to Roger's Performance Marine in Hurricane where the problem will be diagnosed and hopefully repaired. Many thanks to those who responded to my post with advice.
Denny
 

Leardriver

Well-Known Member
Please let us know what the problem and the solution is so that those of us with Bravo 3's can tuck it into our forgetful knowledge bank.
 

shanewave

Well-Known Member
I am experiencing the same problem in my Merc Bravo. Even after the seals were changed last year...so, for now, I just top off the gear oil every few days.
 
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