Late last year I got stuck at Santa Cruz when my Optimax 175 took a major dump. The tow boat captain who brought me back strongly recommended Mike at Dick Core Marine in Santa Paula, as he keeps their fleet up and running and, as you'd expect, they run their Optis hard.
It was a bit of a wait to get the boat in for service (Mike operates out of a single bay hanger at the Santa Paula airport) but it was worth it. Not only did he fix the immediate problem (I was afraid the motor was toast), but he also corrected several underlying issues that had been overlooked by previous Mercury techs.
Mike is a nice guy and *really* understands these engines backwards and forwards. If you can justify the haul up to Santa Paula, it will be worth your time and effort.
Dick Core Marine (805) 525-8044