Always scared to crack a block so I double winterize mine. Pull all the frost plugs out of the Merc 5L and drain then put plugs back in. Run 4 gallons of RV antifreeze through the block and pull the plugs again and drain block exhaust and pump. Put plugs back in and park it in the shop. May be a waste of antifreeze but it make me feel double safe and it's cheap and easy to do.
There are at least three different draining sysyem's listed in my manual.....I drain the water, hook an air compressor up and blow out the stuff that can sit in spots, change the leg and engine oil, add fuel stabilizer.
Some fog the engine, I never have....
The boat sits in a shop most of the winter, but does have to go out if, I need the shop space....never had a problem.....just have to get all the water out....then theres nothing to freeze....
You can pump in antifreeze if you are concerned....
Was in Edmonton Marine Service a year or so ago, they were talking about putting on a winterizing class for the do it yourself group....the owners are or were insructors in the marine engine group at NAIT.
I don't a boat so I have no idea about it but I am sure glad it that time of the year again lol... that means winter is coming back!!!!! Come on winter!!!