1977 Evinrude 85 - Leak at Trim Cylinder Sending Unit

[OldOMC31]

Have a 1977 Evinrude 85hp with the Tilt and Trim cylinders on the outside of the engine mounts. The trim cylinder is leaking where the sending unit bolts to the middle of the cylinder. Don't care about keeping the gauge working, just about fixing the leak.

The attached breakdown (part 37) is the sending unit kit. I believe the plastic bushing is what is causing this.

I seem to remember seeing it on here that someone cut a bolt down to use as a plug but cant seem to find it now. Does anyone know what size/thread plug is needed here to plug this off?

 

[OldOMC31]

I plan to use a plug similar to the attached picture. Just need to figure out the right size/thread pitch. If anyone knows the size, that would be great. If not, I plan to just remove the sending unit and bring the plastic spacer with me to get a correct plug. Just would take longer this way as I don't get to the boat very often.

Hoping to fix before a walleye trip in a month.