Thursday, October 30, 2014

Bottom Paint

After patching the hole left when the through-hull was removed and finding and fixing a few other defects in the bottom of the boat, I needed to get some bottom paint back on those spots so the sea life that likes to make itself home on boat hulls would be deterred.  With all the patches, and since the boat is already out of the water, we decided that I should put a coat of paint on the entire boat.

While we were at the boat show, we checked out a few vendors of boat bottom paints trying to decide what we really need.  There are a variety of paints out there.  There are hard bottom paints as well as ablative varieties.  If you already have paint on the boat, you also need to determine compatability of the new paint with the existing paint.  For instance, you can't put a hard paint over an ablative paint.

Since we already had an ablative paint on the boat and we didn't want to strip off all the existing paint, we needed to choose an ablative paint.  Most ablative paints have copper oxides as one ingredient to deter marine life.  Some also have other chemicals that deter algae and grass growth.  Yet others have additional biocide chemicals.  Recently, new water based paints have appeared on the market that tout easier cleanup with lower VOC content.  It can get rather confusing.

I liked the idea of the water based options due to their easier handling, thinning, and cleanup.  We also liked the more "eco friendly" (if you can call a bottom paint that) concepts of some of the non-copper based paints.  Unfortunately, at $200 a gallon or more, some of these paints I felt were just too expensive for my first foray into bottom painting.  In the end, we decided on Pettit Hydrocoat.  It is water based, claims it can be applied to just about any other bottom paint (and we didn't know what had been previously used), and was the cheaper of the water based paints on sale at the local hardware store for about $150 a gallon.

The lightly sanded and taped off bottom

The preparation instructions on the can said to lightly sand the bottom before application.  The yard claims they just power wash, scrape off any growth and loose paint, and then paint the boat.  I decided I would go with the manufacturers recommendation and lightly sand.  I bought a pole sander, some 80 grit sandpaper, sanding sponges, goggles and a respirator.  Let me just say, in hindsight, I should have picked up a Tyvek suit as well.  The result of sanding is very fine particulates of the old bottom paint and the stuff sticks to everything.  After sanding, I rinsed off the boat to get rid of as much of the dust as possible.

Painting isn't that difficult.  One of the keys is to have the paint well shaken before application and then keep it stirred during application.  Apparently the copper tends to settle so you need to make sure it stays mixed.  First, I took some painters tape to mask off the waterline so the bottom paint only goes where it is supposed to. After using a brush to paint the corners and hard to reach places, the rest of the paint is rolled on with a short nap paint roller.  The Pettit Hydrocoat didn't have any obnoxious fumes and really reminded me of exterior home paint during application...other than the need to keep stirring it.

I applied a couple coats over the patched areas and then put a coat over the entire boat.  The result wasn't perfect (it would probably look better if I did a second coat) but it accomplished the goal.  The patched areas are well coated and everything looks fairly uniform now.  Hopefully this paint will work out OK.

The (almost) finished paint job

I'll need to paint the spots covered by the stands just before we launch the boat, but it is otherwise done.  The new paint is slightly darker than the old paint, so I'm glad we painted the whole bottom.  It does look a bit better now.  It took about a gallon and a half of paint to cover what I've done so far.  Looks like it would take about 3 gallons to do the whole boat with the proper two coats.  Hopefully that, and the sanded paint below it, will keep the barnacles away for a while.

And I definitely learned one thing...if I ever want to strip all the old paint off the boat, I think I'll hire someone to do it.


  1. Looking good. We used Petit Hydro when we first got Smitty. I guess they had problems with the formula that year because a lot of people complained about it. I know the people that went back to Hydro the next year were satisfied with the results again.

    We decided to take the bottom all the way down to fiberglass, apply a couple coats of barrier coat and then repaint. We have been using the Interlux Pacifica Plus (no copper, biocide paint) for the last 3 years and have been happy with it. We got two years out of the first 2 layers. Saned those off last spring and put 3 layers on. We hope to get through until next December with those layers.

    Fair winds,


    1. Hey Jesse,

      Well, looks good from a distance anyway. Should be good enough for my intended purpose anyway. :-)

      I should probably soda blast the boat down and start from the beginning as well, but I'll wait until next time when I have more control of the schedule.

      The Hydrocoat seemed to have favorable reviews, so hopefully that was just one batch from Pettit that wasn't good...of course knowing my luck, probably the cans I bought.

      Take care,