So one thing that generated some interest from my last post was naval rules. Neoclassical Geek Revival already has all the components one needs for a great naval system.
The components you need to know are
Luck Points VS Body Points
"She's a fine vessel"
So the first conceptual thing to know, is to treat the ship like a living being. This means it will need its physical attributes. Its mental and metaphysical attributes (Intelligence, Awareness, Social, Luck, Spirit are the captains)
Strength represents the raw power and sturdiness of the ship. A ship built to take a beating, haul massive cargo or ram other ships, will have a high strength score. This is most important for figuring out how many body points of damage a ship can take.
Agility is the manoeuvrability of the ship. This is used when figuring out the ships initiative (along with the captain's intelligence modifier). The agility modifier will also be used for any attack or defence rolls made by the ship (not people on it).
Health represents the general level or repair on the ship. A ship may be a powerful galleon with a high strength, but it may not have been properly repaired in 10 years. It takes on bits of water, the ropes are worn and there is a bad case of termites. Just like with living beings, health will impact body point total (how much damage the ship can take) and be important for travelling.
"Thar be a storm rolling in captain!"
When people travel across harsh terrain they make health checks to see if they suffer body point loss and wind up dishevelled wretches. Ships are no different (the health of a ship could also be considered its' sea worthiness). But isn't all ocean terrain the same for a boat? Flat water? Not at all, remember that terrain isn't described by its physical make up but by its danger, the physical make up is given as examples. Weather is often the indicator of danger on the high seas. Going through stormy waters in monsoon season is more dangerous than a gentle inland sea.
"Its a big vessel, carries lots of cargo!"
Size modifiers are important, obviously a big strength 16 galleon in good repair (health 12) should be able to take more than 17 points of damage before sinking. Assume a default size modifier of 10 for boats compared to men. I say default because even amongst each other boats will be vastly larger than others.
So "Boat Size 1" is "Human size 10". A sailboat would be "size 1" (for a boat) while a galleon might be size 10 (for a boat). This is important if the two damage each other through ramming. Its also important for calculating cargo that can be carried (see encumbrance). Don't forget that cargo is probably stored in containers, not floating loose.
An important note is that damage from weapons are based on the size of the weapons. An easy assumption to make is that "large, medium, small" weapons are also size 1 (for boats). Be their ballista's, catapults, or cannons. Use weapon tags as appropriate.
"Fire at will!"
Combat will almost certainly come up. An important thing to note is the difference between the ship attacking something and people on the ship attacking something. The general line of thumb is who is doing the aiming? Things like broadsides or rams would be the ship attacking, turrets would be the gunner attacking. Defence rolls are almost always made by the ship.
Note that the ship probably doesn't have very good modifiers, just a d20+agility mod. For a broadside, I would recommend roll once to hit, and then once per gun for damage (get a bingo roller ready).
Grapples and knock-downs are both possible (aka Boarding actions with ropes and grapnel and trying to bump a ship to pull away).
Note the most important point will be the captain, specifically how many luck points the captain has. Remember that luck points are transferable downwards, and the captain can absolutely spend luck points to keep her ship from taking damage.
This is a major benefit of luck points, in some games you can have a bad-ass warrior and be no better than a level 0 commoner once you are in command of a vessel, not so here. Captain Jack will still be damn hard to kill in his ship.