Re: leaks water from hole in thermostat cover plate
Sounds like the poppet valve diaphragm is leaking. It'd probably be a good idea to go in there and renew all of the poppet assembly's rubber parts, and replace the thermostat while you're at it.
Be careful when removing the 'stat cover bolts, if they don't readily break free you're gonna need some heat to get them loosened up.
Coat the cover bolt threads with Permatex No. 3 aviation-type gasket dressing, or waterproof boat bearing grease and they'll never get stuck.
Here's a parts breakdown so you can see how this all goes together:
http://www.mercruiserparts.com/Show...6.png&inbr=3374&bnbr=140&bdesc=Cylinder+Block
HTH........ed
