I’m working on one of these mean green machines right now! Mine’s a ’52 and there are both drain and fill plugs. The drain/fill is on the top of the trailing edge of the skeg, the vent on the starboard side in the typical place. Here’s a photo I took showing the gears, in the shot you can just see the brass drain/fill in the upper left:
Use Lubriplate 105, John Deere Corn Head, or if you have the nice old waxy underwater grease, use it!
I’m working on a page about them for my website – it’s still in draft form and by no means complete, but if it is of help to you here’s the link: http://www.oddjobmotors.com/elgin-16.htm
Let me know how you make out with running it – looking forward to trying mine soon.
Art S.