Boat Bottom Painting

[Gerry Zagorski]

I've been using Interlux MSC multi season bottom paint for the past few seasons and am pleased with the results. Paints that are not multi season loose their anti fouling capabilities over the winter lay up and have to be repainted ever year. This causes build up because you’re painting over a layer of dead paint every year. All you need to do with multi season is paint the spots that are showing through.

The most important part of painting 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 Interlux 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.

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 or 3 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.

If you use the multi season paint then all you'll need to do is touch up the spots that are showing through next spring. This usually takes about a quart of paint. If you don't use multi season the entire bottom will need to be re painted.

As far as the water line you 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 and 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 your stuck putting the boat in the water and taping a line about an inch above the water line while at rest.
Go for the multi season stuff. Speaking of stain lines, the easiest way to get them off is to use a product called On Off... Use gloves and a rag to wipe it on, let it sit for a minute and rise it down with a hose. Be careful not to get it on any metal surfaces as it will damage them, including your trailer.


Bottom line is muti season paints will cost you a few more bucks up front but it’s less expensive in the long run and much less labor intensive.