1971 Johnson 18hp : Flywheel nut thread pitch / diameter?

[KD8NPB]

I picked up a 1971 Johnson 18hp for cheap...the ignition system has been completely replaced, but the crankshaft / flywheel nut is crossthreaded.

This part:
301988 ? NUT, FLYWHEEL (1 required per assembly)

What thread pitch / diameter is the crankshaft?

Anyone know?

I want to buy a split die so I can run it up from the bottom to get it straightened out.

 

[racerone]

1/2-NF comes to mind.

 

[F_R]

Translated for those that don't know, that means 1/2-20