Gear Lube Monitor Overflowing on lube change

whtzom6

whtzom6

New Member
Apr 15, 2021
9
Boat Info
2011 SeaRay 240 Sundancer
Engines
Mercruiser 350Mag Bravo3
First time posting. Been boating and doing basic maintenancefor 30 years+ on our previous boat, a 18 ft open bow Sea Ray with a 4 cylinder 120 hp Bravo1. Recently upgraded to a Sea Ray 240 sundancer with a 350 mag bravo 3 sterndrive.

Just executed my first gear lube change in my Bravo3 sterndrive unit. Read the manual provided by MerCruiser for my 350 mag Bravo3, and watched some YouTube videos as well. Process went well, removed cap from the gear lube monitor, unscrewed drain plug in lower unit, lube drained out fine after opening up the vent hole, waited about 30 minutes for everything to drain out properly. Pumped in new lube and had a spotter watching the monitor tank, I pumped it in until it reached the operating range level on the monitor lube tank but the oil kept rising even though I stopped pumping and ended up overflowing out the top. Is this normal?
 
It is normal for the way you did it, yes. You should have stopped pumping as soon as the fluid reached about a half inch or so in the bottle. Fit the drain/vent screws back in. Then come back a while later and top off.
 
Same here. Those last few pumps after the bottle begins to fill somehow pressurizes the fluid in the drive.
 
When filling the drive from the bottom plug, as it is the proper way, air gets trapped and compresses as the drive is filled. Subsequently, the trapped and pressurized air will cause the oil to overflow until it burps out.
 
When I did this I would leave top screw out on outdrive. Fill until oil comes out of top hole stop put both screws in and finish filling from bottle
 
Blueone said:
When I did this I would leave top screw out on outdrive. Fill until oil comes out of top hole stop put both screws in and finish filling from bottle
Click to expand...
This - I also pinch the edit: gear lube monitor hose with channel locks so that doesn’t drip out.
 
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Just a small sidenote... there's certainly nothing wrong the method that Blueone said. But, there's also nothing wrong with filling till the fluid just starts to show up in the bottle. The main difference is that there's more air to burp out the first way with (possibly) more times checking/filling up the bottle. Either way gets the job done.
 
I should also add that the lube in the monitor bottle never fully drained out, it went down maybe 3/4" from the "Operating Range" line but that was as far as it went. I even tried adding slight pressure into the bottle to see if I could push it down the tube and into the lower unit but didn't happen.

Thanks for all the advice/guidance everyone, much appreciated!
 
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Yep, I learned the hard way to stop when you start to see lube filling in the reservoir. The first year I pumped until it was at the max line and it kept filling and made a mess.
 
OllieC said:
This - I also pinch the edit: gear lube monitor hose with channel locks so that doesn’t drip out.
Click to expand...
It's a good idea to clean the bottle out. Over time, the gear lube in the bottom of the bottle gets gunked up and actually WON'T flow out of the bottle and down the tube, defeating the purpose of the reservoir. Brakleen works well - remove the bottle from the boat.

I usually suck the gear lube out, first. Then I pressurize the bottle with a cap that I installed a bike stem into it. If it's a boat that I do every year, then I know that the gear lube won't have gunked up yet so I don't bother first sucking it out.
 
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