Where do I put gear oil in Merc 20hp?

[junglejake]

Got this 1963 Merc 20hp and as you can see from the pics I can only find one screw at the bottom to put oil in through. The only other screw is at the top but it says "Fresh Water Flush" right above it with an arrow pointing to the screw. So my question is where do I put the oil in the leg and how?

Thanks for your help!

 

[corm]

Re: Where do I put gear oil in Merc 20hp?

Hi,
In you 3rd picture the fill vent hole is the small stainless screw just above the cavitation plate. The fill hole is on the bottom of the gearcase nose, it is the same size as the freshwater flush plug. Fill it from the bottom up to purge out the air in the gearcase. Nice look old girl!

 

[junglejake]

Re: Where do I put gear oil in Merc 20hp?

Hi,
In you 3rd picture the fill vent hole is the small stainless screw just above the cavitation plate. The fill hole is on the bottom of the gearcase nose, it is the same size as the freshwater flush plug. Fill it from the bottom up to purge out the air in the gearcase. Nice look old girl!

Got the fill vent hole on the bottom, but do you mean that the "Fresh Water Flush" plug is where I put the oil in? Or do I take out the fresh water flush plug and fill it through the fill vent hole close to the cavitation plate?

Cus there is only one plug at the top of the shaft and its the fresh water flush plug...

Thanks for your help!

 

[corm]

Re: Where do I put gear oil in Merc 20hp?

Hi,

The fill hole is on the bottom of the gearcase nose
Just below the centerline of the propshaft in the front of the gearcase.
The fill plug is larger than the vent plug screw. Tip the engine up and look at the bottom of the lowerunit. You will see it easier then.

The freshwater flush plug is for water. You basically use this if you run it in saltwater. You run a garden hose into it to flush out the saltwater.

 

[junglejake]

Re: Where do I put gear oil in Merc 20hp?

Found it (I think)! Please see the pic. Is that the right holes?

 

[lprizman]

Re: Where do I put gear oil in Merc 20hp?

correct,,fill till it starts coming out the top,,then put in the top plug,,then the lower one,,forms a vacumm
get new gaskets for each screw if you haven't already