From the way I understnad it, but am not for sure. The cooland runs through
my Mercruiser motor and thorugh a huge cylider on the side. Water from the
lake also flows through this cylinder to cool the cooland, like a natural
radiator. Is this a good description of how it works?

My other question is, my coolant on the overflow tank can be half way
between the add and full lines. My temperature while running is at 175
(right in the middle) where it always is and what the manual says is
normal. Now with the engine off and cool (or hot) if I open the cooland
tank cap you cannot see any coolant in there.

I added a couple cups of coolant into the tank and within a short time it
came out into the overflow container. Temperature still remained the same.

I was just wondering if its normal on closed systems to not see any coolant
in the metal coolant tank that is up by the top of the motor.

--Cameron