Interlux offers three basic types of bottom paint.
Hard epoxy is maybe the most popular, and Interlux BottomKote and Ultra are examples.
Ablative paints are also somewhat popular, and oddly enough they named one such paint Fiberglass BottomKote. So if you buy BottomKote, its a hard epoxy, but Fiberglass BottomKote is an ablative. How confusing is that?
Other examples of Ablative paint is Micron.
The third kind is a thin-film paint, VC17 (which is what I use).
One issue with paints is that you generally have to stay with the same type, or in some cases, the same brand of paint. If you use hard epoxy, you normally need to continue using hard epoxy unless you completely strip the paint off. While there are some crossovers allowed, it varies with the old and new paint. Interlux has a compatibility chart to aid in the changing of paint.
One exception is VC17. It is not compatible with anything but itself.
Most paints use copper, or cuprous oxide as the active ingredient. If you ever had a fish-tank, you know that if you drop a penny into it, the fish will die, as copper is toxic to most marine life.
So most paints differ in their delivery of the cuprous oxide.
Hard epoxy has copper mixed in it (well, after you mix the paint prior to application). When you apply it, the copper is in suspension. It works by the copper slowly leaching out of the paint. However, after all of the copper has leached, the paint sort of resembles a sponge with holes where the copper used to be. This can absorb water, and adds to the weight of the boat.
It is usually recommended that after a few years, the paint be stripped off to keep the weight down. My last boat used this kind of paint.
The advantage of the hard epoxy is that it is low drag, and can be burnished for less drag.
The second kind of paint - ablative, also has cuprous oxide in suspension, but it acts like exterior house paint, as it chalks with use. So as you run the boat through the water, new paint (and copper) is exposed. The advantage here is that the paint strips itself clean, so there is not nearly as much buildup. The main disadvantage is that it is a soft paint, so there can be more drag. (I have not used this paint in any of my boats).
If the boat is on a trailer, some folks prefer the hard epoxy, as it seems to scratch less than the ablative paints. But one rule to remember is that there are dozens of paints, each with its own features, so its hard to characterize that one type does this, and another type does that.
The third kind, a thin-film paint, is represented by VC-17, and as far as I know, is unique to the industry. VC-17 is a hard teflon film that has a very high degree of copper content. It works by oxidation of the exposed copper. In this case, the copper is on the surface rather than in suspension. As well, marine life cannot attach itself to the copper.
One nice thing about VC-17 is that it also contains Teflon, so it has the least amount of drag of any of the bottom paints, and its the paint of choice for racing sailboats. The paint, being thin-film, will not build up significantly over the years, and is by far the easiest to apply.
To apply a coat each year, simply clean the hull (no sanding required), and paint again.
Since VC-17 is a fresh water paint, it is very popular on the Great Lakes. It is used on probably 90% of the sailboats, but maybe only 5% of power boats. Seems many power boaters have not yet found the advantages of the low-drag characteristic as sailboaters have.
The advantages are less drag, and often the paint results in no loss of speed over unpainted hulls. There have even been reports of a gain in speed over unpainted hulls, but its likely the unpainted hull has some marine growth on it for this to happen.
The major disadvantage is that VC-17 is limited to fresh water use, and it is not compatible with anything else. Also, it is often necessary to prep the paint with a barrier coat or it won't stick properly to the hull, so the first application of the paint can be a bit expensive. Another disadvantage - maybe, is that when you apply the paint, it goes on copper, making your boat look like a Duracell battery. But after a couple weeks in the water, the paint oxidizes and turns its pre-determined color, which is either Red, Blue, or something called Original - which is a brown/black color. So another limiting factor is the colors of choice you have. This is the paint I currently use.
There are also additives, such as Ingarol and Biolux, which basically do the same thing. Some bottom paints have the additives and some do not.
While basic bottom paints do prevent marine growth, they do not necessarily prevent algae from attaching to the paint, so you can still have a green scum line on the hull. While the scum doesn't stick and is easily knocked off with a brush, it is still another neccessary maintenance chore. Ingarol and Biolux are algaecide additives and are supposed to prevent this. I have used both additives in the paints I have used, I have found Ingarol to be much less effective than Biolux.
Calling Ingarol and Biolux an additive is almost a mis-nomer, as they are pre-added at the factory. You don't get a little bottle of Ingarol to add to the paint.
Well, you now know about everything I know about paints I have used.
Interlux also offers a paint called TriLux, which does not use copper, so they can make it in white. I have not used this paint, so I am not sure what the active ingredient is, and I have not much comment to offer.
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"Yesterday's Dreams"1995 Carver 325 Aft Cabin 
Posts are amateur opinion only. You assume all responsibility for any action you take as a result of reading my posts.
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