Yanmar 2QM20 Transmission Issue

[zoic100]

Help!! I have a 2qm20 1982 Yanmar in a Endeavour E32. The transmission coupling flange is attached with a machine nut that is holds the coupling to the spline shaft off of the transmission. When I put the transmission in Rev the nut threads off of the shaft, there is a wrench that fits the nut, but is 300 to 400 dollars and very hard to find. I made a tool out of an old socket and can get it to a point that I felt that it would hold, but after using the Rev a few times it spins off. I have tried Locktite and other produces, but this did not work. Can you help.

[nv5l]

The end of the threaded spline should have a groove, looks like a shallow keyway. Once you tighten the nut, use a cold chisel to stake it, i.e., there's a lip that protrudes out beyond the nut that can be bent in with a cold chisel to keep the nut from spinning off.

[nv5l]

Here's a drawing you might find useful:

http://www.soverel33.com/Boat/Engine..._PunchNut.html