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Bottom Coat - It's coming OFF!

Jun 1, 2016
Hunter 28.5 Lake City, MN
Last Saturday, my son & I went up to our boat to try a number of things, to get the bottom coat off our 78 Hunter 28.5. For the most part, it only has a black ablative coating on it. I have put several coats of Interlux ACT on the bottom, but I'm not sure what the previous owner(s) put on, though I suspect somewhat the same.

Last year, there were a few spots that had chipped off, so I scraped those areas off and put on one or two coats of Interlux 2000E as a barrier coat, and them another coat of two of ACT. I had decided at that time that this year, I should strip it all off and redo the bottom.

So, Saturday the idea was to try a bunch of things, to see what would work, and what wouldn't.
Tried a sander (50 grit) with a vacuum for the dust
Some citrus stripper (though it was recommended NOT for fiberglass. May try it yet on the keel).
Also tried a sharpened putty knife scraper.
Tried the scraper with a heat gun as well (peels off, rather than scrapes, not nearly as clean!).
Lastly, we tried a Sawzall with a scraper knife.

It was the sharpened putty knife (1.5") that worked the best for us. What we learned was that the scraper had to be VERY sharp. As a matter of fact, we typically sharpening them about every 10 minutes or so, with a flat sharpening stone (and some water). The coating comes off reasonably easy as you scrap, through not all the time. Different areas seem to react a bit differently to the scraping. Sometimes it's a bit harder to get off, and takes a bit more work to chip it off, but for the most part, we found that we could scrape off LOTS of material in long strokes where the coating was thinner. Thicker portions took a bit more work. We scraped for about 3 hours on Saturday and probably completed at least 20% of the bottom. I worked on it again today for another 2 hours but didn't make quite as much progress (I'm 70, not quite as spry as I used to be!).

To keep the boatyard happy, we put tarps down on the ground to collect the scrapings, and use a vacuum for the final cleanup. It's going to be a lot of work yet, but not NEAR as bad as trying to sand it all down. I'm guessing that the bottom will take us about 10 hours. I'm a bit more skeptical about using scrapers on the rudder, but I'm sure that we'll try it. May just use a course grit sander on the keel, and hopefully some 5200 to help the "Hunter Smile".

I did try the Sawzall blade (4", though they do have a 2" that might work too), which I sharpened as best as I could. It worked kind of OK, but you couldn't remove near as much material as with the putty knife blades. I was a bit concerned about it digging into the fiberglass, but with the blade at a steep angle (sawzall close to the hull) it didn't seem to dig in. I seemed to ride up on the top of the coating, rather than take it off.

The few spots where I put on barrier coating last year, comes off quite a bit harder. I may just leave them as is, and put another coat over the top of those few areas.

Plans are for 4 barrier coats of 2000E and 2 coats of Micron CSC.

Hope this helps someone to get the bottom coat off their boat...
I know that every bottom is different, so your mileage may vary!

Sir Michael
  • Helpful
Likes: Ward H


Jun 3, 2012
Hunter 33 Steamboat Wharf, Hull, MA
I shake my head when I watch boat owners and yard workers applying a new coat of bottom paint every Spring. Eventually they will all be where you are. Most of us have only one bottom scraping job in us, then never again. Suggest you use a multi-season ablative and only re-coat about every four years. Touch up as necessary in between. You will never have to do that job again.
Jun 1, 2016
Hunter 28.5 Lake City, MN
Roy, that's what I'm hoping for. The Micron CSC is supposed to be multi-seasonal. I strongly suspect that with the barrier coat, I'll never have to remove it again (maybe somebody else in xx years!?).

Sir Michael