Get motor up to temp.
Close drain plugs.
Hook up muffs to 5 gallon jug off anti-freeze and run it till it comes out back of boat, or until jug is almost empty.
Pull hoses at top of thermostate and fill them with anti-freeze, as a precaution.
Leave muffs hooked up, and put a cap on hose end, to prevent any water from working its way into the drive.
No idea if this would work, in my head it does BUT.
Maybe Mike has a opinion.???