Bryan,
The block heater is part number 2358980 and is listed as: Engine Block Heater For 135, 155, 165, 169, 180, 186, 187, 195, 220, 240, 226, 276. It may be used in other applications as well. It replaces one of the threaded plugs on the right (exhuast) side of the engine block. I think there are two, and I used the rear one because it was easily accessible. There is another number on it as well 1034, and HH7. I have no idea what those numbers mean. The list price at the Yanmar dealer was $36.82