Exactly. The drain plug on those coolers is really tough to get at. What I do is disconnect the raw water inlet hose at the thermostat housing, hold it down to drain the hose. There is a water drain on the port side of the pivot housing on the transom mount, if this is not clogged, it should drain that hose and cooler. But, to be on the safe side after draining it that way I then hold the hose up and fill it with marine AF till it runs out the outdrive water intakes. I have not had to get at that drain plug ever since doing it this way.
