My boat sat for a week in the water with 40 deg temps during the day and 20's at night. The water temps were in the 50's. The engine room acts as a cooler and insulates it to a certain degree.

I will admit I was nervous but she fired right up a week later.

My mechanic was a little slow getting around to winterizing, so my boat was on the trailer for a few nights where it was 28
or 29 or so, which made me very nervous. But it was fine, it is winterized now.

Just saw this thread.....the original poster has a cruiser (I had them for years) and no one mentioned all the other systems in those types of boats

-Fresh water system (tank, pump, hoses, faucets)
-A/C...if it has one has water that stays in the lines and a sea strainer
-Toilet, someone did say porta-pottie, but he likely has a full vacu-flush system
-generator, also has water cooling lines and a sea strainer


these ALL hold water that needs to be dealt with.....some of them are MORE likely to freeze before the engine will.