coolant drain plugs 1968 merc IO 80

[KevinBergstrom]

I am winterizeing a 68 Starcraft with a mercruiser 80 and can not locate any coolant drain plugs on the block or head. I removed the small brass plug from the aft end of the ex manifold, the plug on the forward end was seized so I pulled the face plate from the manifold and found it dry.My manual identifies location of drain plug location for merc 60 then jumps to 120 and up no information regarding the merc 80 or 90 can anyone help me locate the block and or head drain plugs for this engine that renault manufactured for mercruiser?