Will my boat be ok? temps getting low again

So I was thinking I was out of the woods with the temp rising here last week and got my boat out to test my new ballast set up and started it obviously. I keep it in a stroage unit which is closed. I wouldnt say its full closed as there is about a 3 inch gap from the ground to the back wall but the front and sides and roof are closed. temp dropped to 30 degrees just a few minutes ago at midnight. So it will prolly be below 32 till about 7 or 8 i would guess. So how low would it have to get out side to bust my block? Considering that it is indoors and the temp should be a little higher than out side. The shop mechanic told me the other day I should prolly be ok but the weather temp has dropped alot and I dont like to deal in maybes with my boat motor.