If it is a screw in type it does not matter.If it is any other type you will want to put it in from the outside so the water pressure will help hold it in if it was to fail.Charlie
If you put in from the outside the water will be trying to push in on it, keeping it there. If from the inside the water will be trying to push it from the hole into the boat. If you're nervous about plugging it from the outside keep your spare handy on the inside, but you'll never need it.
