"Sorry I posted this to the wr
"Sorry I posted this to the wrong thread ealier. I have 1978 Merc MCM 470 that we have just put in the water this year and the closed cooling system is losing coolant and starting to overheat but we cannot tell where it is going, not in the bilge. Engine is running fine and pulled 3 plugs and they are burning nicely. also no water in the oil. How can we test the 3" heat exchanger yes, still a 3" in there, to see if there is a crack in the unit and allowing the antifreeze to get out there. Compression test was good. There is also signs of steam coming out the back of the boat at the engine. Where else would the coolant be going? We appreciatre the help. as we are only on this Island (Pender Island, B.C.) for 2 more weeks."
"Sorry I posted this to the wrong thread ealier. I have 1978 Merc MCM 470 that we have just put in the water this year and the closed cooling system is losing coolant and starting to overheat but we cannot tell where it is going, not in the bilge. Engine is running fine and pulled 3 plugs and they are burning nicely. also no water in the oil. How can we test the 3" heat exchanger yes, still a 3" in there, to see if there is a crack in the unit and allowing the antifreeze to get out there. Compression test was good. There is also signs of steam coming out the back of the boat at the engine. Where else would the coolant be going? We appreciatre the help. as we are only on this Island (Pender Island, B.C.) for 2 more weeks."