I had a 2" seacock for the exhaust port on my last boat (36hp).

I used to close it for winter storage. Forgot to open before starting the engine in the spring one time. No damage, but the "O"ring sealed swivel fitting on the Vetus waterlock let go with a very loud BANG. Was able to just reassemble the fitting and open the seacock.

Never did it again.

Have a 3" exhaust on current boat, no seacock or valve, but good height on the loop and I can access the drain valve on the waterlock if needed. The loop is the same height as the cockpit drains, so if I see water there, I plan to open the waterlift drain.

I will just stuff a rag in it for the winter.