Winterizing a merc 135 hp 4 cylinder 1/O

I have had ski boats in the past and know how to winterized a V-8 inboard, but nor sure on the little 4 I bought. It's a 1990 4 cylinder alpha 1 merc. I can see no drain plugs or petcocks. I was going to pull the hoses off the thermostat housing and pour in antifreeze and then down the pickup line into the drive(third smaller hose on the thermo housing). Drain the lower unit oil and take the battery out. I am just worried if this is enough for the block to be safe. I know there are some I/O owners out there so please help.