Cold doesnt bother Fiberglass unless you start immersing it in liquid nitrogen. But cold can cause engine problems if you dont warm it up reasonably. Many a merc has died when hammered while cold, going back to the early 90s and the 200 EFIs, continuing with many of the optis…Only problem I would worry about is “water in closed spaces”. IE the speedo can freeze since water runs from the pitot to the analog speedo (if you have digital, no worries). If you leave water in the live well which could have water trapped in the plumbing, pumps and valves, that could be an issue. Just make sure drains are open and boat is stored level or nose-up to get water out.2008 Pantera Classic2014 Mercury Pro XS 200