Drain plug on 2005 mercury mercuiser, 496 motor

[birdman1234]

I would to think there is drain plugs on this 496 motor with closed system to drain coolant from the motor, but I am unable to locate just one. I have two side by side so it is hard to see under or on the side of them. Not a lot of room in my 2005 Formula boat. Can you help me? No one in Florida want to work on it so I am giving it a try.
Thanks

 

[04fxdwgi25]

There is a 1/4" NPT plug on each side of the block, down low, by the oil pan rail close to the center of the engine.

 

[alldodge]

Welcome
What is your serial number?

and your wanting to change the antifreeze?