How to Redo the Bottom Paint and Epoxy Primer on your Aluminum Boat

One of our big projects on this boat was replacing the bottom paint. We had no clue how old the bottom paint of the layer of epoxy underneath was and no clue if water had gotten between the epoxy coats and the aluminum. If it had, then the water would be turning acidic and breaking down the aluminum which would have put us in a world of hurt.

So, in the yard we decided to grind off the bottom paint to save ourselves money and save the epoxy because after testing a section, the epoxy layer looked like it was in fairly good shape, and we may have been able to just patch some areas. Boy, were we wrong! As we started grinding off the old bottom paint — it started turning gummy. We then realized that someone in the past had painted epoxy paint over top of an ablative then they had put on the ablative that we were trying to grind off. So essentially, on the bottom of Tangaroa was a layer of black soda epoxy, then a bright blue and a yellow ablative bottom paint, then another layer of epoxy, then the bright blue ablative top layer. All in all, I counted 7 different layers though in some places it was more and, in some places, less.

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The grinders were NOT working. We then had to make the choice to bite the bullet and get the dustless marine blasters back to blast the bottom! It was a nightmare. We had just blasted the hull for 12 days and now we needed them back.

It took another 3 days of blasting to take off as much bottom paint as they could. They still could not get down to aluminum which meant days and days of grinding with 40 grit sandpaper. Josh came over and between the three of us we grinded — and grinded — and grinded. The black soda epoxy caused our skin to feel like we were sunburned even though we were covered with all the Protective Equipment you could imagine. We even had ski goggles on that I found at a second-hand store. Josh was a trooper though however he did state it was the worst thing he had ever done.

After a full 4 days of grinding — 8 hours a day — we were there. Tangaroa was ready for an all-new bottom! We consulted with Strait Marine, and it was decided that we would use Interprotect 2000E which was a top-of-the-line epoxy primer for wood, fiberglass, aluminum, and steel boats. Now how many coats would we need?

We consulted with the painter for Strait Marine and determined that specifications required 8 coats to bring it up to the appropriate thickness. Now you may say 8 coats is too many however we DID NOT want to do this again while we own this boat. So, if the specifications say 8 coats — we will put on 8 coats.

We started by cleaning the hull with soap and water and made sure all soap residue was off. Then it was time to mix the two parts and paint! I would start on the forward port side of Tangaroa and start making my way around the boat. It would take approx. 3 gallons of paint and 2 hours. After I completed the coat, I would rest for 1 hour then apply another. I put 2 coats of light grey on the first day then began filling all the holes and corrosion spots with 3M Marine Premium Filler. It was easier to see the spots that needed filling after the primer versus filling before primer. So why did we fill all these spots? These are spots that marine life can get their little tentacles into so we wanted to make sure the hull was as smooth as possible.

After filling, I put on a coat of white Interprotect 2000E. I switched colours to make sure that there was good coverage. I sometimes mixed the white and grey together also to make a light grey. I found that the grey made a thicker coat than the white so preferred to use the grey as much as possible. After two more coats — it was time to fill again and sand off those areas.

Then if was back to painting. I put the 7 coats of epoxy primer on over the next 4 days. We had to time the last coast of epoxy primer and the first coat of bottom paint though for good adhesion. The Strait Marine professional painter told us to put the first coast of bottom paint on 2 hours after the last coat of epoxy primer. Now it took me over 2 hours to paint the hull so with Blaine there, we had to time it. I started painting the epoxy primer and 2 hours after I started, he started the bright blue bottom paint and followed me. As we are an aluminum boat, we could not use any bottom paint with copper in it. Copper and aluminum DO NOT MIX. We chose to use Interlux Tri-Lux II bottom paint.

We used the bright blue bottom paint as our indicator coat. If our bottom paint started to wear, then the bright blue would be visible and then we knew that we would have to apply more bottom paint.

Once the bright blue was on, we put on two coats of black. I had to wait to put the two coast of black on above the chine because I was also painting on a nice dark red boot stripe. All in all, we applied 22 gallons of paint to the bottom of Tangaroa. It was expensive to purchase the product however since we did it ourselves, we did not have to pay for labour.

Now we just must maintain it and if we had not been hit with so many ice floes this past winter that damaged our waterline bottom paint, we would not have to come out of the water to paint for two years.

I hope you enjoyed this and if you would like to see the video of our project and follow along with Tangaroa’s refit, subscribe to youtube.com/onboardtangaroa.

Also visit www.onboardtangaroa.com for more information on all things Tangaroa.

Cheers

Blaine, Janis, Josh, and Izzie