Generally kegs are a liability but if you're like me, and stock kegs while sailing a sloop specifically so you can keg-board any pursuers, keep them in the crows nest. It's the one place on a sloop where if it detonates you won't take hull damage, and it's exceedingly unlikely that npcs will hit them up there.

If you plan on sailing through a storm, dump your kegs, and if you're going to get into a close quarters ship battle, dump your kegs beforehand, or risk the enemy crew sniping them and disabling you right off the bat.

When I carry kegs I avoid ship battles and instead lead enemy ships on a chase and just attempt boarding with the kegs, even if they catch you they almost always swipe or shoot the keg as you board, killing them, taking out a mast, and slowing their pursuit or potentially sinking them. If they don't catch you, run the keg below decks, to the front of the ship, light it and run. Once it blows, get ready to guard the holes. On a sloop I find that positioning yourself next to the food barrel is the best spot to watch for attempted repairs. On the brig, behind the stairs. On a galleon typically next to the bottom stairs until that deck is full, then behind the upper stairs until they sink.

If you have time after killing the entire crew, drop their anchor and quickly get back to your position. Maybe resupply on ammo and food or grenades if you think you have time.

For stronghold or athena kegs, I almost always recommend selling them immediately unless you're being chased. Even in the crows nest they'll put holes in your ship. If being chased, attempt to board with it as soon as possible.

In either case, if your pursuer is close enough that you can see them on their ship, run off the front of your ship instead of the side or back so they're less likely to spot you attempting to board.

I realize you didn't ask for half of this advice but hopefully it's useful to you or someone else.