I realize this post is a year old but I have just had this same issue happen to my upper starter mounts on my moster 185. Sheared completely through and badly gouged out their mating surfaces on the carter support.
I had to replace some parts on my starter a few months ago so I seemed to have made the mistake you have pointed out here.
I got a new carter support and starter mounts coming, but my question is: how firm do I torque these mounts/spacers to the carter support before I finish attaching the starter assembly with the securing bolts (this time holding the mounts steady with a spanner)? I can’t find a torque specs for these mounts in manuals. Are they just hand-tight?