I haven't seen it mention yet, but always make use of their supplies if you can.
While you may not have any fire, that doesn't mean they don't. Obviously, it goes case by case. Check their barrels for fire to increase burning, but realize that fire takes a lot of time to actually be destructive to the boat. Your best case is to monopolize their food barrel to deny their ability to fight while on fire.
Also, sometimes crews will carry kegs. Make it a habit to check their crows-nest. If you are able to acquire a keg, don't just drop it immediately for a quick boom. If their is multiple, by all means drop one to add to a later chain. However, ensure to place the primary explosive in the furthest position. For a galleon this means the bottom deck towards the front. This makes players travel the furthest to plug said holes.
If it wasn't an outpost, make use of the terrain. Forts are usually great to plop holes.
Don't expect most of these to work, it usually takes quite an oblivious team to solo one up a large group. However, its low risk on your end, so have it.