Sounds like cracked thru-hull fitting, maybe over tightened. Just installed ST60 through hulls in same C&C model, will double check for leaks at launch this week.
Call Ray @ Ray's Marine Systems Inc. 905-451-3285, best to call 9 am sharp as he leaves office no later than 10:30 for site visits. He is Raymarine authorized dealer and might have part in stock. Not sure where you are, he is in Brampton, ON Rays Marine Systems