Bottom Painting Tips

[Gerry Zagorski]

Won't be long till it's time to launch the boat again and figured I resurect this article I wrote on Bottom Paint.

I have a friend who pulled his boat this year and although he used a good quality bottom paint, he still had tons of barnicles. He did not use the boat that often so I'm sure that had something to do with it. I've heard people adding things like cyan pepper to their paint.. If any of you have any tips to offer up to help reduce the barnicle growth please post them here.


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. It costs you a few more bucks up front but it’s less expensive in the long run and much less labor intensive.

[BRM247]

I am bottom painting for the first time and thought sanding, base coat, multi-year ablative was the way to go. A painter suggested to avoid sanding and after removing the wax to go with a self etching primer then a few coats of multi year ablative. Was sold as a cheaper/cleaner alternative resulting in a smoother finish with less drag. Downside is that you are unable to return the bottom to its original state. (I guess you can't sand blast the primer off). Was told that this is becoming popular in NJ with just the need to re-apply a top coat as needed in 2-3 years. Anyone have any experience with self etching primer instead of sanding a new bottom to prep for a different type of base coat? My research shows that this is primarily used on aluminum bottom boats.

Thanks

[Gerry Zagorski]

I have no experience with the self etching primer. One thing to consider though. Smaller trailerable boats with out bottom paint are much more desireable in the used boat market. If you intend to sell the boat in the future, stripping the bottom paint off might get you more money for the boat. Does not sound like this is an option if you use the etching primer.

[BRM247]

I hear you on the resale but that is not a major concern at this point plus it can be argued that a large percentage in the northeast prefer to have the bottom painted already when looking for used in the 24 foot range. Pro's and cons to both and will be debated forever, I just need to know if this stuff really works as advertised. Thanks for the info.

[irishc]

I never used the self etching stuff but i did overhaul my boats hull in March of 2000. I've averaged 6 season between repainting... Some seasons i don't even have to touch up anything so stick with what Mr. Z says... Sometimes it is worth it to spend a little more time and money initally than to experiment and have to spend more later to fix a mistake/problem. Sanding and applying barrier coat followed by a bottom coat of one color finished off with 2-3 top coats of your desired color is the way to go. I won't lie, it is alot of work and money initally but the returns and rewards are worth it. I have a 20 footer and it takes me litterally 20 min and a 1/2 quart of paint to get the boat bottom ready for launch at the beggining of the season.

[BRM247]

Thanks, no sand etching primer got some bad press on another site, I'm definately going to sand. Your 1 qt 20 minutes is just touch up work each year until you think the entire bottom needs to be redone? question, at that point are you taking anything off before applying or just adding over top?

[Gerry Zagorski]

Yep - Just adding over the top. I have a 25 foot boat and it usually takes no more then a quart to do the touch up. The paint usually wears more on the chines and the running surfaces of the boat when you are up on plane.

If you have any barnicle growth make sure and get it off and skuff the area with a scouring pad before recoating.

[CaptBob]

Prep and the Proper paint are the key

We scrape and wire brush the hull, then wash down bottom with on/off-water mixture.

Paint use the best you can, I use Interlux Micron Xtra with VOC, yes it is pricey but we get ZERO GROWTH ON THE BOTTOM.

We touch up the worn down spots with a brush and then paint the whole bottom after the touvh up.

Only growth we get is on the trim tabs and a light slime line at the water line.

Remember when you buy your paint, YOU GET WHAT YOU PAY FOR!

[Gerry Zagorski]

Are you using multi season paint Bob? If so, why do you choose to recoat the entire bottom?

[CaptBob]

Gerry,

It is stated that it will last for 2 seasons. But as the paint reacts with the saltwater to "polish" away the growth I prefer to repaint each season, especially being as I am in the water from April into December.

I would rather take the extra step to ensure that no growth occurs.