Bottom Painting

[Gerry Zagorski]

Well, it’s that time of year when we start prepping our boats for the spring launch. My least favorite job is bottom painting so I thought I’d share some tips.

There are a lot of choices out there when it comes to bottom paints in terms of brands and types of paints. I’ve been using multi season ablative over the past several seasons and am very pleased with the results. The 2 brands I’ve used are Interlux and West Marine and have not had any issues with any sort of marine growth.

Ablative paints do wear off over time releasing new layers of antifouling capability through the season giving you good protection. Multi season means that the paint will not lose its antifouling qualities over the winter layup. Single season ablative paints wear away as well however, they lose their antifouling capabilities over winter layup so you to have to repaint the entire hull each spring. This means more work, more paint and over time you wind up with multiple layers of dead paint on your hull. The fix for that is stripping or soda blasting your hull and that’s not a fun or inexpensive job.

Multi season ablative is the way to go because after the winter layup, all you need to do is touch up the areas that have worn through. Multi season costs more than single season paints but in the long run you actually save money since you don’t need to repaint the entire bottom and you won’t wind up with multiple layers of dead paint on your hull.

If you are planning on switching over to multi season ablative paints, make sure and go to the paint manufactures web site and be sure the new multi season paint is compatible with the paint you have on your hull. General rule is ablative single season to ablative multi season is fine.

Now let’s talk about painting a bear hull with bottom paint for the first time.

First thing you need to do is establish the water line so you know how far up the hull you need to paint. If you are lucky, you'll probably have some stains on the boat which would indicate how far up you need to paint. It's a good idea to paint about an inch up from the stain line. If you're in a slip you’re likely to keep more stuff on board and when you have a full tank of fuel the boat will sit lower. If you don't have a stain line then you’re stuck putting the boat in the water and taping a line about an inch above the water line while at rest.

The most important part of painting anything is surface preparation. If you don't do this right the paint will not stick so take your time and do it right. Here's what you do.... Make sure the bottom is free of dirt, wax, grease etc. You can use paint thinner for this. Once this is accomplished get some 80 grit sandpaper and a random orbital sander and scuff the bottom. Make sure and remove all the sanding dust for good adhesion.

Next thing is to apply a barrier coat. This seals the hull from water intrusion, which over time can cause hull blistering.

Now apply 2 coats of paint with a roller. Not a bad idea to go over chines and corners with an extra coat as this is where the paint usually wears first. Some people go as far as using one color for the bottom coat and another for the top coat… As the top coat wears away you can clearly see the bottom coat color coming through and you will know exactly where you need to touch up the paint next year.

Multi season bottom paints = less paint, less money, less work + more time for fishing 