With the advent of harpoon cannons on every ship, the rowboat has become less useful. No longer do you need to load everything onto a rowboat and row it back to the ship; you can just aim the front of the ship at the loot and grab all the loot/barrels/whatever.
So the rowboat needs new functionality. I suggest adding a smaller harpoon cannon to the rowboat. It will be mounted to the front, and able to pick up loot. It will not be able to pick up barrels, but will be able to draw itself to them (because the boat is too light to attach them)... although this is up for debate.
The real utility this adds is that it can be used to bind yourself to other ships, which gives it some raiding utility.
So in conclusion: add harpoon guns to rowboats so they are no longer useless and add additional utility.
