I am having problems finding the thermostat for my 582 grey head, the rotax dealership sold me a thermostat for a 583 but that did not fit . The part number that was mentioned #18-3558 I cannot get from our napa dealer and did a little research online. The number seems to bring up a thermostat for marine engines, is this the same thermostat you guys are using? Also does it fit into the existing outlet housing on the 582, thanks for any input. In the mean time I'll keep using the duct tape to block off part of the rad.