Trojan Boat Forum

I need to redo my bottom paint this spring. It's really thick, chipped, cracked--lots of coats. What's the best way to get all the old stuff off? Sand, strip, sandblast. ...?

Also, the bottom paint is 8-10" above the water line. ..Would like to take it down 6" or so--the gel coat isn't smooth under that part

I had mine soda blasted. As to having it that far above the waterline, that may well be a problem. If they did sand the gelcoat properly before painting with the bottom paint, when you remove the bottom paint, the gelcoat may be in bad shape. I have tried stripper and sanding on previous boats and it was painful and a horrible mess. This time I paid to have it soda blasted and it was worth every penny.

Yeah, they did sand above the water line...I was thinking for that part I'd sand it smooth and paint it the boat color. Maybe a stripe at the transition.
I haven't looked into the soda blasting. Best to have a professional do that?

IMO, if it's really old and really thick in places, and if you can afford to do it, you might as well have it blasted, and come back with new barrier coat and anti-fouling paint. A couple thousand bucks, but you end up with nice smooth bottom that benefits in both performance and economy. Then you'll just need to roll on new anti-fouling paint every several years down the road.

'Soda' blasting just refers to just one blast media a blasting contractor might deem appropriate for the job. A qualified blaster might do it with silica sand as they did for me 12 years ago. $450 bucks and I had a blasted gelcoat bottom ready for roll-on barrier paint and then roll-on anti-fouling paint, which are both easy DIY.

The worst part is getting the old stuff off. IMO, let someone else do it. Rolling new stuff on is easy.

Some marinas have rules against blasting (or bottom stripping in general) because of environmental concerns, so check out what you will be allowed to do before you get too deep into what you want to do.

I stripped mine a few years back. Tried using a commercial stripping system (Peel Away - you apply stripper to the hull then lay out paper panels over top. The paper seals things in and keeps air / oxygen away from the stripper, so it doesn't dry out and can just eat away at the paint. Idea is that after 24 hours you just peel the paper off, and all the paint comes with it). Had to special order the stuff (in Canada anyways... got it through a Sherwin Williams paint store).

Didn't work for me, but don't know if it is a product issue or 'environmental'. Might still be worth a try for someone who can control their environment a bit better.

The storage shed my boat is in for the winters has a roof that leaks like a sieve (don't get me going on the city ownership of the shed and that they refuse to repair or maintain it). After I applied product and paper to half the hull, it rained... Rain dripped on the boat and ran along the deck and down the hull sides ..... getting in behind the masking tape I had holding the paper in place. So... I ended up with the stripper, diluted with a few gallons of water, being held against the hull by the sealing paper barrier.... until the paper gave up and the whole thing collapsed (almost on top of me). A couple hundred square feet of paper and stripper came crashing down about 2' from where I was laying...

Anyways.... long story short..... after a bugger of a job of cleaning all that mess up, I manually sanded the entire bottom and sides down to glass with 80 grit paper on a big sanding block (8-10" x 3-4" drywall sanding block). Entire job (with time lost with failed stripper system, and final painting (4 coats Interlux Micron CSC)) took about 100 hours. Sanding is a bugger though - after sanding I was blowing blue snot for a week. Socks I wore have been washed a gazillion times since then, and are still stained blue...

If you hire someone to blast, make sure they aren't too aggressive, or they can damage the gel. Get someone who blasts boats and has good references - don't just get someone who knows how to blast as blasting fibreglass / gelcoat is very different than blasting metal parts or brick... If you decide to sand yourself, make sure you have proper protective equipment for eyes, nose, mouth, ears, etc... And be ready to throw the clothes away.

I paid about $35.00 per foot to have it soda blasted. You can use any media, but soda is not as aggressive as sand. It left me with a paint ready hull. Like said above, the painting is the easy part other than rolling it on over your head while lying on the ground. I tried the Peel Away on another boat and it did not work at all. Ended up sanding the boat with the same mess others have stated. This is one job you should pay to have done. Then roll on the bottom paint yourself.

I had the bottom of my boat blasted last fall. They used crushed walnut which looks like the cereal farina(farina is known to us old guys). The boat is an 86 an never had the bottom addressed.Twenty eight years of paint build up. I thought I would sand the bottom but after a couple hours, I gave up. There are provisions taken by the blasting companies as to reclamation of the media and your boat yard may have it's own regulations. Best check with them first. I am happy with the decision and in the spring I will do the barrier coat and bottom paint procedure.

I had my previous boat done after 40 years of paint buildup. The cost was around $2200 to have it totally redone; blasted, primer, barrier coat, and bottom paint. Still looks fresh after 3 seasons.

I'll definitely do the priming and painting myself, I'll see what my marina says about the blasting. I'm guessing no problem--I just talked with a guy that had it done a couple years ago. All sounds good, thanks!

Getting the bottom soda blasted tomorrow. Do I need to barrier coat it then bottom paint, or does it depend on what I'm left with after the soda blasting?

Definitely barrier coat.

If you have it down to bare fiberglass, I would not skip the barrier coat. The cost of epoxy barrier paint is not too bad in the overall scheme and to not do it and later have blistering would be many times more expensive. I have used the Interlux system before. The only problem is that you have to put on multiple coats when they are not completely dry in between. Depending on weather and size of the boat, you may be painting almost continuously so be prepared with some extra help in case you get tired of rolling paint on over your head. If you let the paint get too dry, you will have to sand in between coats. Follow the directions closely.

Ugh, the soda blasting didn't go well. After working on it for an hour, he says the paint is too thick--it would take him 3 days and hundreds of pounds of soda and WAY more $$ than what he quoted me. I knew it was thick--that's why I was willing to pay to have it done. I showed it to him also. ..
Not sure what I'm going to do at this point