Garboard plug/drain

[Viper]

That is what you call the liability free response from the manufacturer If you have rain (or snow) getting into the bilge of a bigger boat, there's something you need to address whether on land or in the water. Most boats up here also get shrink wrapped over the winter so pulling the plug is not that much of a concern.

[km1125]

Source of the post ....
Leaving a seacock closed during the winter up here will result in a haul out shortly after launch next spring to replace a cracked seacock. Seacocks must be left open over the winter to prevent that as water can collect and remain behind the ball in the valve. Leaving the valve open will allow any water to drain over time. Some valves will have drain ports in them but leaving them open will accomplish the same thing.
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That actually happened to me about 20 years ago. While I was still in the water prior to hauling, I blew out the through-hulls of water and then closed them. These were the original OEM gate-valve style valves. There was no water collected above them, but there was water trapped behind the gate, which expanded and cracked the valve and I found it when I was relaunching. Luckily, I had enough time to run to the store and get a ball valve to replace it while still in the hoist, and continued with launch that day.