2001 Mercury 115HP Saltwater - which hole should the gearbox oil come out of?

twr7cx

Petty Officer 2nd Class
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Apr 6, 2008
Messages
148
Today I drained and refilled the oil in the gearbox on my 2001 Mercury 115HP Saltwater outboard. I refilled it from the bottom drain hole using a hand pump. I undid both top plugs (one is marked 'VENT' and the other 'OIL LEVEL'). When refilling the oil came out of the VENT hole not the OIL LEVEL hole. Do I need to refill it with the plug in the vent hole?




 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,415
Done correctly.-----------Let it sit for a while and make sure there is oil at the oil level screw.
 

MercGuy

Petty Officer 2nd Class
Joined
Jul 20, 2006
Messages
195
I will probably create a furor by saying this, but I always fill mine from the top "vent" hole.

It is so much simpler and cleaner than trying to fill from the bottom.

When filling from the bottom you may have to switch oil tubes if the one you start with isn't completely full, and then there is the joy of pulling the tube away and trying to thread the screw in while oil is rushing out.

Instead, I purchased a new, clean oil can with a tip that easily fits in the vent hole. I pump the oil can and refill it as needed. when oil starts coming out of the "level" hole it's so easy to casually add the top two plugs.

I've been doing that since 1999 on this engine, and before that with my prior boat, with no negative effects that I'm aware of.

Just my $0.02.

Thanks,

-Steve
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,778
I had a '02 90 with 3 holes. Manual said to insert pump in the lower hole with both vent plugs removed and pump till you have oil coming out the front vent hole. Install that screw and continue pumping till it comes out the aft hole and plug it. Then remove the adapter and quickly install the drain screw. Engine should be in the vertical position for the process.

Edit: Ensure each screw has a sealing washer. I always used the OEM blue fibrous washers. I have heard that there is a new type out that is yellow silicon molded into an aluminum retainer. Haven't seen any of these. They are supposed to be reusable whereas the blue are recommended to be new each time you use them.

Mark
 
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