In theory, your boat is tilted bow high and has drained out.
Its not a water pipe full of water. No water to expand when it freezes to crack it.
You plug the fwd to aft pipe? You rely on the fwd bilge pump to clear the bow? I don't like that...
I have no plugs. Any water drains aft on plane. Some sits in fwd when at rest but pumps when the fwd float switch kicks.
Problem I had on my old V20 was that decades of crap was blocking up the front end of the pipe, slowing down the flow, and there was no access to it without cutting the floor of the fishbox
A garden hose to the aft end would clear it for a while. Anything that goes into the cuddy deck drain is there forever. In the V20, the fishbox drained to that space. Think Striper scales....and everything they puke up... I ended up using that space for storage. removed the bottom and added a second bilge pump there.
I think a lot of old boats have that problem. Many boats have the same "pipe under the tank space" configuration.
My 265 has acces to the front of the pipe in the cuddy. There is a fwd bilge pump and also a shower sump.
