I have a 1984 H34 with a fresh-water cooled Yanmar 3GMF, and plan to drain and replace the coolant. I find a drain tap on the rear of the heat exchanger tank. But I haven't found a drain tap lower on the engine, to drain the coolant from the block. There's a flexible hose hanging from what looks like a drain location on the lower port side of the block. But there's no valve at that location. Note that I also have a hose running to and from a hot water heater under the dining table aft settee, which uses heated engine coolant to achieve its purpose. Anyone with this engine figured out how to drain the coolant? Tips appreciated. Thanks.