Mid twenties is not that big of deal. It takes a while for things to freeze at that tempurature and it's not going be cold for very long.
Hook up a hose, fire it up, let it run for a while - then throw a blanket over it.
If you still have worrries put a small elctric heater in the boat, or near it, away from any source of fuel or vapors. Along as it's above 32 degrees in the garage/boat - no problem.
edited to add: Plug in a fan along with the heater and there's no way you'll start a fire then.
Last edited by fish head; 04/03/11.
