YES it is, I've worked on many, many, marine out-drives and used stainless thread-serts and stainless hardware correct drill size is of UTMOST importance !
I will order a time-sert kit for 6m and go with the stainless inserts if they have them, unfortunately i have a few 6m to repair. Former mechanic did some work on it and lost the 6m and jammed standard bolts in place.