The heat exchanger has been pressure tested twice, no leaks. Yet when I run the boat, my starboard engine is eating coolant. None in the bilge, none in the oil, but I can smell it in the exhaust. Rate of loss seems to slow as the day progresses, but it can lose one to two gallons in a day of running. We keep it topped off by adding every hour or so, but know this isn't the way to operate. Anyone have any suggestions on where to look?