Here In Boston Is't Been Ice Nipple For A Month! The Way I've Always Done It(and The Other 300 Boats A Year At Our Marina):
6 Gallons Of -50 Non Tox Anti-freeze(the Pink Stuff From Any Rv Store) Into The Engine Block/exhaust/cooling Hoses. C.r.c 656 Or Wd-40 Sprayed All Over The Outside Of The Engine. Get A Pint Of Marvel Mystery Oil Start Your Engine, Warm It Up A Little And Put About 4 To 5 Ounces Of The Mystery Oil Right Down The Carb. Just When It Starts To Really Smoke Shut The Engine Off Quick!(to Keep The Oil In The Cylinders 'til Spring).( If You Have New Merc E.f.i. See Your Dealer Don't Use Marvel!) When You Re-commission The Boat In The Spring Don't Worry About The Non-tox But When You Start It Up For The First Time Your Neighbor Might Run Over To You With A Fire Extinguisher Because For About 5 Minutes That Boat Won't Even Be Seen There Will Be So Much Smoke! Works Every Time And You Maybe Spent $25 Bucks.
I've Found That If You Have A Few Days Of Around Freezing Or Below There Is A Danger Of It Freezing. We Had One Last Week That Was Lucky Because The Engine Only Blew Out 2 Freeze Plugs, But I Have Seen Them Where You Could Fit Your Small Finger Into The Block Crack! Winter Is A Crazy Thing You Hear Stories Of Freezing Temperatures Were They Have'nt Heard Of Anything Like That For Decades. Just My $.02 Worth. Merry Christmas To All!...bill.