I have a 1978 crusader 270 hp (350 cu in ) with a closed cooling system. My firsr time out I notice that the antifreeze/water was low, so I filled it up. When i first started the engine there was some antifreeze that came out in the wet exhaust. I open the radiator cap to check the level and top off with water will the engine was running. the level stayed up while the engine was running. I idled at the dock for about 1/2 hour. When i shut down the engine I could see the level in the radiator go down. I look in the bilge but found no water or antifreeze. The temperature stayed at approx. 165 degrees. Any suggestions what might be the problem?