721 Simundson Drive ▪ Point Roberts ▪ WA ▪ 98281
Phone: 360-945-5523 ▪ Fax: 360-945-5525
Beneath the surface – Caring for the hidden parts of your lady:
In this article I will attempt to answer some of the most common questions regarding
protecting the underwater portions of your boat. I will cover different paint technologies,
how to paint underwater metals, special care for sterndrives, sacrificial anodes (zincs),
barrier coats, stripping, blisters, and costs for both DIY and full service paint jobs. Done
right, a full paint job can last several years with only quick hauls or a diver to change
anodes along the way. Hopefully this will help you to plan for proper maintenance of
your boat’s hull and make for an enjoyable experience on the water.
Painting the Hull – What Paint to Choose?
Since tributyl tin was banned several years ago, almost all antifouling paints today use
copper as their primary antifouling ingredient, and several add Biolux (a pesticide) to aid
in slime control. But they do it in different ways. I will discuss Interlux brand paints
here because that is what we sell, but other manufacturers use similar technologies.
Hard Paint
Unless there is a particular reason to use a hard paint, I always recommend against using
them. Fiberglass Bottomkote is the classic antifouling paint of years past. It is relatively
inexpensive, effective, and lasts 1-2 seasons before needing to be recoated. The problem
is that hard paints work by holding the copper in a hard binding agent. As the copper
dissolves away, the paint loses its effectiveness but the binder remains behind. As more
coats are applied the dead binder layer gets thicker and thicker until it starts to flake away
in large unsightly chunks. It is very difficult (read: expensive) to remove the old dead
paint. With the added costs of more frequent haulouts to repaint and eventually the high
cost to strip the bottom, I believe that in the end hard paints are the most expensive way
to antifoul your boat. The two exceptions are painting some underwater metals
(discussed later), and high-end racing finishes such as Baltoplate. As I am not a sailboat
racing fanatic I will not presume to debate the finer differences between racing finishes,
but we have at least two racers using Baltoplate and it is a beautiful finish when done
right. Please talk to me if you need this type of finish and we can discuss what you want
done.
721 Simundson Drive ▪ Point Roberts ▪ WA ▪ 98281
Phone: 360-945-5523 ▪ Fax: 360-945-5525
Ablative (Sloughing) Paint
With the exception of the very cheapest versions such as Bottomkote XXX, I
wholeheartedly recommend almost any ablative paint over a hard paint for a fibreglass
hull. With ablative paints, all of the paint dissolves over time, leaving you with a clean
hull ready for repainting. The main concern I hear is that people fear that it will rub off
too quickly, especially if they have high speed boats. I simply have not seen this to be a
problem. You may need to add a single coat along high wear areas such as the bow, but I
have seen many high speed boats get three or more years out of their ablative paint job.
Pressure washing annually refreshes the surface layer, and does not seem to shorten the
life of the paint significantly. I really like ablative paints, and stock three types:
Epoxycop Ablative – This is our entry-level paint. It is cheaper than our hard
paint, and a good choice for a do-it-yourselfer on a budget. It is made and backed by
Interlux, and seems to be a good paint. It is marketed as a single season paint, but if you
bought it you are likely on a tight budget and will probably stretch it for two seasons with
extra pressure washing in the second year.
Micron CSC – Available in several colors, we stock this paint in red, black and
blue only but can have any color you want in about three days. It was the previous
owner’s top selling paint by a large margin, and for good reason. A good two-coat paint
job generally lasts for three years with very little growth and it will go over most other
paints with very little preparation. You can expect to see minor slime growth in the
warm water of the marina, but it washes off easily and the paint overall performs very
well. If the surface layer becomes “dead” from disuse of the boat, a quick pressure wash
will restore the effectiveness of the paint.
Micron 66 – This is Interlux’s top paint, and I have been very impressed with its
performance. Slime buildup is minimal. Reports are that it lasts a long time, but I have
only been using it for one year now and can’t confirm that yet. There are two advantages
that account for the 20% cost increase over CSC. It contains Biolux to help with the
slime buildup. More significantly, this paint actively reacts with and dissolves in the
water even if the boat is not being used. This helps maintain effective antifouling
protection for boats that may sit idle for long periods of time. Other ablative paints need
the sloughing action of the water flow to refresh the surface and can begin to foul up if
the boat is not used, even though the paint is still good. The biggest problem with this
paint is that it is not as compatible with other antifouling paints, and often needs a primer
coat to seal off the old paint. The primer is not expensive, but we generally give the hull
a good sanding if we add the primer, and the labor to sand the hull and add the primer,
plus the extra materials costs, generally adds several hundred dollars to the cost of the
job. On a fresh bottom, or over Fiberglass Bottomkote, I almost always recommend this
paint. Over Micron CSC or an unknown paint, Micron CSC is often the better value,
particularly if you are hauling frequently anyways or are a very active boater.
721 Simundson Drive ▪ Point Roberts ▪ WA ▪ 98281
Phone: 360-945-5523 ▪ Fax: 360-945-5525
Underwater Metal
Painting underwater metal properly is a very time consuming process, and the various
metals react differently to the copper in antifouling paint. Propellers and shafts have the
added stress of very high water speeds and forces applied to them.
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Stainless steel (such as trim tabs): When coated with antifouling paints, the
electrochemical reaction between the two metals causes the paint to simply fall
off, usually within days or weeks. To get the paint to adhere, our process is a
complete cleaning to bare shiny metal, followed by one coat of Vinyl-lux prime
wash, four coats of 2001E epoxy barrier coat, and then your favorite antifouling
paint. If the barrier coat is not chipped, painting in years to come should only
require antifouling paint.
Bronze (rudders, struts and thru-hull fittings): Technically these parts should be
treated the same as any other metal, but because they are very high is copper, we
see passable results from people who choose to simply paint over them with
bottom paint. If not bonded well, there is a tendency to see some “burning” of the
paint around these parts.
Aluminum: Aluminum is a special case, because if not treated properly, the
copper in the antifouling will set up a reaction that quickly destroys the
aluminum. Essentially the aluminum in the hull or drive acts as a sacrificial
anode and works to protect your paint! We have seen hulls boiling with corrosion
when improperly painted. The proper treatment is the same as for stainless steel,
but with extra care in the prep work. When finished, use an antifouling specific to
aluminum, such as Trilux III. This antifouling is not as effective as other paints,
but it is formulated to be much more compatible with aluminum.
Propspeed
We have recently started applying Propspeed to running gear. Despite what they may
claim, my experience is that it is only appropriate for your propeller and shaft. It does
not have any antifouling properties per se, but simply creates a slick, rubberized surface
that repels growth. But if the part is not moved regularly, growth sticks anyways. Trim
tabs, thru-hulls, struts, etc simply do not get enough water flow to knock growth off.
Preparation is meticulous, but the finished product has gotten good reviews. I have not
seen the performance over time yet, but I am optimistic given other feedback I have
heard.
721 Simundson Drive ▪ Point Roberts ▪ WA ▪ 98281
Phone: 360-945-5523 ▪ Fax: 360-945-5525
Sterndrives – Special care
Sterndrives require particular care. They are a mix of several different metals, with
precision seals and expensive aluminum housings that are easily destroyed with neglect.
Particularly troublesome are the popular Bravo 3 and Duoprop models. The twin
stainless steel propellers will quickly destroy a drive through galvanic corrosion if the
zincs are not changed religiously every year. Many owners choose to change zincs on a
Bravo 3 every six months. We have a propeller zinc upgrade kit that helps, but constant
attention to your anodes is important. Drives should be painted yearly with two full spray
cans of Trilux III, and touch-up of primer is generally needed as well to cover any nicks
or scratches. Spray the paint before you change the anodes and you will save yourself the
trouble of masking the new ones before painting them. Drive oil needs to be changed
annually as well, especially if the boat is moored. This allows a check for water getting
past the seals before major damage is done.
Anodes (Zincs)
Sacrificial anodes can be made of zinc, aluminum, or magnesium. They must be checked
regularly to make sure they are still tight and have enough material left to protect your
boat until her next haulout. Magnesium is not appropriate for salt water and would
disappear within days if used here. I was sceptical of using aluminum as an anode until I
realized that both Mercruiser and Volvo send their drives out with aluminum anodes from
the factory. It is noticeably cheaper than zinc, and is perfectly effective. It is worth
noting that it is a different alloy than the aluminum used to build a drive or hull out of.
We carry both aluminum and zinc anodes, mostly because there are a few customers that
simply are not satisfied with anything but zinc.
Barrier coats
The barrier coat we use is Interlux 2000/2001E. It is a two part epoxy coating that was
originally marketed as a waterproof barrier to protect porous gelcoats from blistering.
We generally use it on new boats as an added measure of protection, or to seal a bottom
we have had to strip. We also use this product as the primer for painting underwater
metal. Read the directions carefully and watch the overcoating times.
Blisters
Other articles abound discussing the causes of blisters, but my general advice is this – if a
blister is less than the size of a Loonie, ignore it. I have never seen a boat sink because of
blisters. They are unsightly but very time consuming to repair properly and don’t
generally cause other problems. If your lady’s bottom has cellulite, I suggest that you by
$4000 worth of your favourite beverage. Every time the blisters start to bother you, go
have a drink. I’m pretty sure you will be a happier person in the end.
721 Simundson Drive ▪ Point Roberts ▪ WA ▪ 98281
Phone: 360-945-5523 ▪ Fax: 360-945-5525
Costs
Haulout: $8 - $10 per foot. This includes your haul, pressure wash, blocking and launch.
Tarp fee: $25. This is for the tarp we provide under your boat. It is a one-time cost.
Lay Days: $20-$25 per day. Aside from being among the cheapest anywhere, we only
charge for two days if we are doing the work. This can represent a significant saving vs.
doing the job yourself, especially if you are the type to haul only when it rains for a week.
Painting supplies: $65-$85. We probably cost more than if you do it yourself, but this
also includes the gloves, coveralls and protective gear that many DIY painters skip.
Paint: $135 - $250 per gallon, and you get what you pay for. A typical 36’ boat will use
two gallons for a full two-coat paint job.
Zincs: Don’t forget these! Not changing them regularly is probably the most expensive
maintenance item you can skip. A small sailboat may only have one $6 anode, a large
powerboat may have $150 worth.
Labor: This varies widely, depending on what you want to do and if you have kept your
lady clean. The painting itself generally takes 2-4 hours per coat, obviously varying with
boat size, but also with the form of the bottom. High speed boats with many chines and
edges take longer – a smooth sailboat hull goes comparatively quickly. Prep time is also
difficult to estimate without seeing the bottom and knowing the old paint. If we are
putting Micron CSC over itself, we do almost no prep. Some boats get a light adhesion
sand and others need far more. Cleaning up trim tabs, shafts, and props can take hours,
but if you then barrier coat and antifoul them you will have an easier time of it in years to
come. Zincs take a few minutes each to change. Our labor rate for painting is $56/hour.
Propspeed: We charge $80 per prop and shaft for the materials, and prep time really
depends on how big it is and how clean, but we are careful to take the time to get things
really clean, or you are wasting your money. It takes about thirty minutes to apply.
Sterndrives: Budget $300/yr for us to change the oil, antifoul and change zincs.
Obviously an Alpha leg is a little less than a Bravo 3, but not that much.
Thank you for taking the time to read all of this. I hope it helps you.
Sincerely,
Ben Lazarus
Service Manager