About a million or twenty years ago, more or less, we purchased a Catalina 25 from a very thrifty and DIY oriented Scotsman. He had a time of it with the original outboard motor power on the boat and converted it to the OMC saildrive system himself. In true DIY and thrifty Scotsman fashion, he made the exhaust system and loop after the waterlift muffler out of PVC pipe with only a small flexible piece of hose to the thru hull at the transom. When I first saw the system it was after we had used he boat for the summer. I thought it was carzy but it turns out the exhaust was cooler, much cooler, that hot water coming from a hot water tank. We sold that boat and as far as I know the owner still has it and still has the same system in place.