Head Bolt size

[makomike1]

I need to know what size the head bolts are for a 1995 112hp Johnson. One of my head bolts stripped the head and I need to put a sleeve in . Thanks Mike

 

[racerone]

They are 5/16-NC thread.----And why did this event occur ?

 

[makomike1]

They are 5/16-NC thread.----And why did this event occur ?

The previous owner over tightened head bolts.
What type of Heli coil do you recommend??