Gear lube reservoir empty...

LUnaCY

Active Member
Aug 28, 2018
206
Afton, MN
Boat Info
310 Sundancer 2002
Engines
Mercruiser 5.0 MPI Bravo III
I think I know this answer, but let me have it.

Mercruiser 5.0 MPI I/O

I winterized, changed gear lube, filled reservoir. Idled 3 hes to new marina. Gear lube reservoir is empty.

Im certain the plug is in.

Complete lower?
 
If you don't have an oil slick behind your boat it might have just been an air pocket that finally worked it's way out. Fill it up and see if it leaks out again.
 
Did you fill it from the bottom plug?

Even when I fill mine, it drops a little after an hour or so and I have to top it off with a few ounces.

You could just have a larger than normal air bubble that purged itself or a leak in the hose from the reservoir to the transom.

I would expect a large oil stain in the water if you lost that much from a leaking seal.

Top it off and check again.
 
I did fill it from the bottom, then cleaned and topped the reservoir. Mech was kind enough to chat with me a bit. Said dont sweat it and top it off. At worst keep topping it, but hes seen as much as 1.5 reservoirs burp out. Good to know. Its also nice tgat its no wake, I have 2 engines, and only plan on using a 10 mile stretch of tge river. Ill update as I find out.

Thanks all! I was thinking it was a $5k morning.
 
I did fill it from the bottom, then cleaned and topped the reservoir.

That part sounds like you filled it from the fill plug (bottom) till the oil showed up at the vent plug (top). THEN you stopped. Then you added oil into the reservoir. If that's true, as others were mentioning, that's the issue right there. When you fill a system that has a remote resevoir bottle, you CONTINUE filling till the oil shows up in the bottle. In your case, there was a lot of space still unfilled between the top of the drive and the tube/pathway to the bottle.
 
My BIII did the same thing. I just had it re-sealed for $600, not too bad. But they do "burp" when re-filling oil from the bottom plug. Usually 1/2 Liter or so.
 
That part sounds like you filled it from the fill plug (bottom) till the oil showed up at the vent plug (top). THEN you stopped. Then you added oil into the reservoir. If that's true, as others were mentioning, that's the issue right there. When you fill a system that has a remote resevoir bottle, you CONTINUE filling till the oil shows up in the bottle. In your case, there was a lot of space still unfilled between the top of the drive and the tube/pathway to the bottle.
This may be it. Only 1 engine had the issue...i cant remember if i waited until it came to the reservoir before i topped the reservoir. Anyway... i think im good.
 
The burping has me troubled on mine too - I think the mechanic is bs'ing me! Am I wrong.... Had both drives pulled and sealed. $$$. After running for the weekend, I noticed the reservoirs were higher than when we started. They removed some fluid and said normal burp after major service. A burp should make it lower not higher in my mind! Am I wrong
 
The burping has me troubled on mine too - I think the mechanic is bs'ing me! Am I wrong.... Had both drives pulled and sealed. $$$. After running for the weekend, I noticed the reservoirs were higher than when we started. They removed some fluid and said normal burp after major service. A burp should make it lower not higher in my mind! Am I wrong
Gear lube can heat up - especially in the Bravo III. Its not uncommon to see the fluid rise after some good runs. Or, it could be a bubble that is working it's way out, but hasn't yet gotten to the surface. A bubble would expand quite easily in size due to heating up, thereby raising the fluid level.

What was it like after it cooled down and you checked it again?
 
Well, I topped the reservoir and have idled 4 more hours with minimal res fluid loss. Behind the boat there was a bit of a slick while drifting but not bad, and Im not sure it was even from my boat. Im comfortable idling around as its no wake everywhere in the river and will keep an eye on it.
 
Gear lube can heat up - especially in the Bravo III. Its not uncommon to see the fluid rise after some good runs. Or, it could be a bubble that is working it's way out, but hasn't yet gotten to the surface. A bubble would expand quite easily in size due to heating up, thereby raising the fluid level.

What was it like after it cooled down and you checked it again?

Fluid was still high and dark like it was hot. There was some water in fluid but mechanic said it is holding pressure fine so can't be the seals he did. Must be something else he doesn't have to warranty.
 
Water in the fluid? That can’t be a good thing..........
If not a seal, then how else did it get in there? How good are those drain and vent plugs and their gaskets?
 

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