"Ree-Yees" wrote in message
.. .
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?


Good enough. That "cylinder" on the side is properly referred to as a heat
exchanger. It does the same job that the radiator on your car does, it
transfers the heat from the coolant to something else. On a car, the
radiator transfers the heat to air. On a boat, the heat exchanger transfers
the heat to the sea water.

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.

It is not unusual, but I would not expect that to be normal. I would
suggest replacing the radiator cap (heat exchanger cap?). The cap should
be identical to the type used on older cars, available at any auto parts
store.

Rod