Sea Ray

Try looking behind the microwave. Found it there on my 41 Dancer.

I'll check the switch...start with the simple things. The head blower is somewhere on the port side. Our galley is on the starboard side so I highly doubt it could be behind the microwave.

I have 3 in my 450 one in the guest head one in the nain head and one in the galley on the port side. I believe the blower for the port head is in the back of the sink/vanity although i have not confirmed that.

On my 420 the head blower and galley blower are on port side so could be in galley

Just in case anyone is curious...on our 1999 Sundancer 450 the main head is on the port side and the galley is on the starboard side. The blowers for the second head and the galley are, of course over there behind the refrigerator.
The port side head blower is behind a small panel at the back of the medicine cabinet above the sink. The opening is about 8" X 4". Very limited access. super difficult to get out. Had to blindly find the mounting screws and get them out. Next challenge was getting the blower out of the access hole. Had to take it apart before it would come out. Anything you drop is likely gone (there's a flashlight down there that is probably running out of charge right about now).
Super difficult but not impossible.

On my 500DA it is behind a panel in the medicine cabinet, crew Quarters

Krobel is right. He forgot to mention to use a 3 inch small phillips screw driver.