Johnson 200 lower unit bolts

[nitsuj]

Hi all! Working on a mid-90's Johnson 200 Ocean Pro. One of threaded holes holding the lower unit has stripped. Helicoil to the rescue! Problem is, I can't get a handle on what size these are. When measuring with a pitch gauge, it seems to be 16 tpi. It doesn't fit in any of the metric gauges. When when trying to run a die on the bolt, a 10mmx1.5 die seems to fit best. A 7/16x14 tpi also fits. Anyone happen to know for a fact what size bolt this is so I get the right helicoil?

edit: according to a parts diagram, it’s 3/8x16. That die doesn’t want to easily thread on the bolt, but it will snuggly thread on. Maybe the bolt is stretched a bit. Seems the mystery is solved, but I can’t see how to delete my thread.

Thanks!