FiberGlassics® would like to thank Jamil Mehdi for this article.  This content is copyrighted, and cannot be reproduced without permission in any form without written permission from the author.


This article is about how to paint a boat, but it's more than that. It's about how to take an ugly duckling and turn it into a swan. It's about the catharsis of accomplishment. It's about reaching for the brass ring, that elusive perfect boat. And most importantly, it's about patience and comprehension. The patience to do it all, the comprehension that not only is it being done right, but knowing why it's right.

So here it is, Part One: Surface Preparation. Part Two: Priming and Top coating will follow as soon as I've written them. I'm not going to delve into the forum with follow up questions until Parts Two and Three are complete, because I anticipate most questions will be about steps further down the road. Thanks for your patience in this regard. Enjoy.

Prepping For Prep work

The first step is to wash the boat. Inside and out. Wash it like your mother was coming over. Wash it like you have Obsessive Compulsive Disorder. Wash it, then wash it again. Cleanliness and organization are the keys to success when painting a boat. It may sound like “a good idea” to keep things tidy, but not really necessary at this stage, but that's not true. Working with a clean palette speeds up every element of prep work and helps to keep you focused.

Next, take pictures of your boat from every angle. This is going to help you out immensely when it comes time to re-bed hardware. It's also nice to have some “before” shots. Take more pictures than you think you need and take them from weird angles. Get inside the boat, lie on the floor and take pictures of the underside of things. Take as many pictures as you can. You will be glad you did for reasons that are not yet apparent to you.

The "Before" picture. Not bad from 20 feet away, but not a yacht.

The next step is removing the hardware. For this I like to have two drills handy, one chucked with a #2 Phillips and the other chucked with a #2 Slotted. In my pocket I also carry a small bit case with #1 and #3 Phillips and Slotted as well as square drive bits. In my other pocket is a small adjustable crescent wrench.


The hardware removed from the deck.

A stack of sandwich-sized and one-gallon Ziploc bags are essentials. All hardware and their fasteners should be individually bagged and labeled with a Sharpie. An extra hour of work here will save you ten hours later when your digging through a bucket of random hardware and screws trying to decide what goes where.


The hardware bagged with their fasteners. I don't intend to reuse the fasteners, but now I will know what to replace them with.

Side note: There are only three metals that can be used as fasteners on a boat; 316 Stainless, 304 Stainless, and Silicone Bronze. Half of the fasteners I removed were rusted out nickel plated garbage. Even if you don't intend to paint your boat, replacing fasteners with marine-appropriate metal is always a good idea

Where you stop with the hardware removal is limited only by your motivation, your available space, and your confidence. The goal here is to have a completely unbroken work surface. Ideally, the hull will be separated from the deck, the steering removed and all the hardware bagged and labeled, leaving you with two pieces of oddly shaped but otherwise impediment-free fiberglass.


This isn't always going to be possible. It's up to you to decide what's feasible. Just know that for everything that stays on the boat, you will have to sand around it half a dozen times, you'll have to fair around it, and you'll have to prime and paint around it a number of times as well. In the end, one single cleat left on deck can add up to three hours to the total time involved. If it takes you less than three hours to remove it, you've already saved some time.


You should now have a work surface that is free of obstacles. You should also have outlines of dirt and grime where the hardware was attached, but where your initial washing didn't reach. Yup, that's right, go ahead and wash it again. It's OK, I'll wait.


Done yet? Good. Let's move on.

Solvent Wiping

Disclaimer: As with any chemicals or airborne particulates, protecting yourself should be your primary concern. Material data sheets are available for just about every product used in boat refinishing and it is a good idea to familiarize yourself with them. Many have been shown to cause cancer with prolonged exposure, so always follow any recommended safety procedures. At a minimum, always wear nitrile, or other solvent resistant gloves, have good ventilation, protect your lungs, and protect your eyes. If extra protection is required at any step, I'll mention it, but otherwise, I assume you are already following the basic safety steps.

All fiberglass boat that were made from a mold will have traces of mold release wax in the gelcoat. Even 60 year old boats. Marine paint systems are incredibly durable, user friendly, and beautiful when properly applied. However, they are notoriously finicky and problematic when compromises have been made. The smallest trace of wax residue can ruin a paint job, causing fish eyes and compromising the adhesion.


Simply sanding off the top layer of gelcoat will not prevent catastrophe. Wax particles will adhere to the paper and just be ground further into the gelcoat. The surface needs to be cleaned with a de-waxing agent. Awl-Grip sells a proprietary product named Awl-prep specifically for this purpose. You can use it with no ill effects, but it is prohibitively expensive.


Personally, I use denatured alcohol for de-waxing and I use the two-rag method. Saturate one rag with alcohol and wipe a two square foot area. While the panel is still wet, use a clean dry rag to wipe the panel clean.


You should be constantly changing rags to ensure a clean surface, otherwise you're just smearing the contaminants around. When you're done, do it again, but this time don't completely saturate the rag, just get it damp. This second pass should take care of any streaking that will surely occur.

Making it Flat

Disclaimer: Boats exist in varying degrees of disrepair. Just like golf is actually a game of misses, boats are an exercise in repair. Perfection is unattainable. With that said, some boats are worse than others. For the sake of this article, I have to assume your boat is at death's door, cosmetically speaking. The degree to which you need to improve the profile of your project exists solely within your own mind. No step at this stage is a requirement, but all steps at this stage will have a cumulative effect on the finished product.

The next chunk of your life will be devoted to the elusive goal known as, “fair curves”. The beautiful finish and high gloss of Linear Polyurethane paints (LPUs) are a double edged sword. The paint rewards the time spent fairing the boat and it cruelly punishes those who cut corners here. A boat with wobbles, highs, and lows will look like a fun house mirror once top coated. It will grate on your last nerve every time you see it because you know how much time and effort went into getting it to that point. If only you'd spent just a little more time getting it perfect. If only...


Like all boats, yours will probably have a number of chips, dings, gouges, and mysteriously vacant screw holes. Now is the time to remedy this situation.

Side note: I will actually fill every screw hole on the boat and re-drill them at the end of the project. That way I don't have to discover that one was reamed out or that another was in a slightly wrong position.

Let's start with the gouges and dings and such. Your goal here is to have a smooth-sided tapered groove in fresh glass to fill. A chunk of boat that got left at the dock will probably have a jagged edge. To ensure good adhesion of the filler, you need to grind back the jagged bits. For larger gouges (bigger than a quarter) I use an angle grinder with a flap wheel. For smaller nicks, dings, and scratches, a dremel tool with a cone bit works great. You don't want to remove any more material than is absolutely necessary, but you do want to get into the healthy material surrounding the flaw.

Side note: take a tip from Henry Ford and work like it's an assembly line. Don't grind back a few dings, fill them, then start grinding a few more dings,... Get every ding on the boat in one pass. Keep walking around looking for smaller and smaller flaws. The more uninterrupted work you do here the more your eyes will adjust to the task. Training your eyes is no joke. A disjointed system of moving back and forth between tasks will cause you to miss countless flaws that won't become apparent until the boat is already painted.

When all of the nooks and crannies have been identified and properly ground for repair, the next step is to clean them out. A shop-vac with a brush attachment and a hose twice as long as the boat (so you can work without having to constantly drag the vacuum around with you) is the right tool here.

A side note about vacuums: Cheaper vacuums are loud but suck just as well as expensive vacuums. To me it's worthwhile to have a good vacuum. The Fein vacuum is whisper quiet, has an outlet to accommodate sanders and shuts off when the tool is shut off. It's a luxury, but it's great for nerves that get frazzled by loud noises and the ensuing inattention it causes, but they cost about $400. Once again, a small shop-vac that sounds like a jet taking off is just as effective. Reward vs. cost.

Once the dust has been vacuumed away, you need to wipe the boat again with denatured alcohol. You can individually clean each ding, but you will probably end up missing some. It's just simpler to wipe down the whole boat and know you got them all.


Clean up now. Get rid of the dust, the rags, put the vacuum away, and give yourself room to work.


Congratulations! You are now about to stop removing bits of boat and start adding bits of boat. So what do you add? Well, there are several options here, but not nearly as many options as most people think. Just any filler from Napa isn't going to do it. Everything you do from this point on has to be looked at from the point of view that UV light is going to reach it.


Nothing is as damaging to the boat as UV light. Nothing. Automotive grade products do not have the UV inhibitors that marine products have. Nor are they engineered for the motion, flexing, and abuse a boat experiences on a normal day. This is not a place to save $10.


I use 3M premium marine filler for this step. It is a vinylester product. Vinylester is chemically compatible with polyester, it is less porous than polyester so it's more waterproof, and it shrinks less than both epoxy and polyester. It is pre-thickened and it's catalyzed with the same MEKP cream hardener as polyester.


The other options are a marine grade polyester filler, (which will be cheaper than vinylester) or mixing and thickening epoxy, (which will be more expensive, but stronger – overkill for small repairs in my opinion).

Side notes: I'm going to digress here in a couple different directions, so bear with me and I'll get back to the boat in a minute.

The first direction is about MEKP. It stands for Methyl Ethyl Ketone Peroxide. It is the catalyst used for ester-based resins. It can be in a clear liquid form (as when catalyzing straight resin) or it can be in a pigmented cream form (as when catalyzing fillers). MEK is a solvent and is not the same thing. It won't catalyze anything, but it will cause you to grow a third nipple on your forehead or, at least, give you cancer. MEKP on the other hand will cause blindness if it gets in your eyes. Wear eye protection whenever you are using it.

The other direction is about epoxy. We'll talk about the usage of epoxy later, but for now, I want to stress that epoxy exposure is cumulative. This means that you can use epoxy everyday of your life and be perfectly fine, but once your exposure level crosses a certain point, you will never be able to use it again. Once that threshold has been crossed, symptoms range from rashes to death. If you're going to use epoxy, just take a few extra precautionary measures. Double up your gloves. Buy a set of neoprene sleeves, or even a bib (if you're going to use a lot of epoxy), to keep it away from your skin. And never, NEVER use acetone to clean epoxy off your skin. Acetone will push it straight into your bloodstream. Use soap and water only.

OK, back to the boat. If you are using an ester-based filler, use a cream hardener that is similar in color to your choice of topcoat paint. 3M's filler will come with blue hardener. This is so you can tell when it's thoroughly mixed. Hardeners can also be bought in red and white, (how patriotic). Keeping it on the same side of the color spectrum can actually mean the difference between two coats of paint or three. However, if you use white hardener, you have to be very very careful to ensure it is thoroughly mixed, because you won't be able to tell by the color.


Mixing epoxy is a different animal altogether. The cure time of ester-based fillers can be altered by the amount of hardener added. Epoxy requires precise ratios of resin to hardener. Cure times can be altered by buying faster or slower hardeners. Epoxy generates it's own heat when it cures, however, adding thickeners like micro balloons or colloidal silica will slow cure times down by absorbing some of the heat generated by the epoxy. In general, the thicker the epoxy, the slower the cure time.

Side note: In general, I don't recommend epoxy at this stage in the game. It takes a day to cure while vinylester is sandable in half an hour, and adds no appreciable strength to the boat if you're just filling nicks and gouges. Furthermore, epoxy shrinks nearly as much as polyester, ensuring you'll be wasting another day when you have to make a second pass over everything because the repairs are still concave.

Only mix up as much as you can use in five minutes. This means a golf ball sized dollop of filler and a two inch long ribbon of hardener is probably as much as you'll want to mix up at any given moment.


Make sure you have plenty of mixing boards and mixing sticks available. Tongue depressors and small pieces of non-porous polycarbonate work great. You can buy a sheet of thin Plexiglas for a few bucks at any hardware store and you can make as many mixing boards as you want. Stiff plastic spreaders work for application of the filler.


When applying the filler, you want to press it into the void as you move the spreader across the wound, not drag it across the void. Dragging it has the negative effect of weakening the bond to the substrate. When pressing it in, you should see it rise behind the spreader. That's good. All fillers will shrink a little bit in the curing process. The goal here is to get enough filler in the void that you don't have to do it again, but just enough to minimize the amount of sanding later.


For old mounting holes or screw holes the process is mostly the same. The difference is that you'll need a big countersink. Not the countersink/drill bit combos, but an actual dreidle-shaped countersink. Buy the best, most expensive one you can find. It's only going to cost $15 or $20 so don't scrimp here. It will get used enough to warrant the price.


My beat-up workhorse of a countersink. This thing has been with me for three years.

Fillers are not going to stay in a cylindrical hole. There's just not enough surface area for the filler to bond to the fiberglass. It might look fine if you just fill a hole and call it done, but mere days or weeks later, surely by the first time you use the boat at the latest, your filler is going to fall right out of the hole. For this reason, you have to countersink every hole through the full thickness of the fiberglass. That tapered edge will give more surface area for the filler to adhere, and it also creates a wedge to prevent the filler from falling through.


Got it? Great, now go countersink every screw hole on the boat. It's fun isn't it? Now clean up the holes just like you did for the dings and fill em' up just like before.


The holes countersunk and filled.

Side note: Because this boat was previously painted, and because the paint passed a compatibility test with Awl-Grip, I have to assume it is polyurethane. For that reason, I used epoxy thickened with 410 microlight filler to fill the holes.

Every boat is different, and while this tutorial is comprehensive, you must attack your own boat knowing that you will, at some point, have to adapt and overcome a situation not covered here. Hopefully, this article will give you the requisite basics to be able to do so with confidence.

Side note: Putting a piece of tape on the backside of the screw holes will keep the filler from oozing through and solidifying into a hard blue dangly worm. Just a thought.

Side note: Before I continue, I need to say something about sanding blocks. They are your friends. I have no fewer than thirty different sanding blocks. I don't need all of them for every job, but I would rather have them and not need them than need them and not have them.

For a typical glassic, there are a few I highly recommend. 3M is the king of all things sanding. The Stick-it hand sanding blocks are invaluable. They range in lengths, widths, and hardness. (The 2-3/4” Stick-it Fre-cut gold paper for use with these blocks is also my preference – It's available in grits ranging from 80 to 500). Durablock also has fine sanding blocks and they can also be machined to specific profiles. Regardless of what you use, I recommend, at a minimum, one of each of the following:


    Large fairing board
    Small hand block
    Small soft block
    If you can find one for sale on Craigslist, get the Porter Cable Profile sander. They don't make them anymore because the tool was garbage, loud, and did more harm than good, but the profile bits that came with the tool are fantastic. I've bought two of these, one for $30 and one for $25. I threw the tools away and kept the profiles. For hand sanding small radii, tight corners, and fillets, there are no better blocks out there. What's more, they are perfectly sized for 3M's 2-3/4” Stick-it rolls of sandpaper.


Now that all the holes and dings are filled, It's time to start fairing the boat. Using a hard block and 80 grit paper, start removing 90% of the excess filler around your repairs. The second you see that you're sanding gelcoat, stop. Switch to a soft block that will conform to the boat's shape and finish sanding the repair flush.


Don't use a DA (dual-action) sander for this task. It's too aggressive and you'll end up altering the profile.


When all the repairs have been sanded flush, it's time to move on to the next step. The next step depends on the condition of the boat.


If the boat is perfectly faired already, you're on the verge of applying primer. The next step is to sand the whole boat using 150 grit sandpaper. If this is the stage you're at, don't just run out to the garage and go commando with the sander. Keep reading, because I want to talk about sanding techniques, but not until I've addressed fairing for the rest of us whose boats are not so pristine.


If you have print through, (this is where the weave of the fiberglass shows through the gelcoat), wobbles, (unfaired lines of the boat), or crazing of the gelcoat (hairline cracks throughout the surface), you'll need to fair the whole structure.


Side note: For the purposes of this article, I'm going to assume you're using an LPU. My reasoning is; if you're going to go through all the trouble and expense to get to the paint stage, an extra $200 for paint that can outlive you is a small price to pay. If you're going to use a single part poly, you'll just have to extrapolate the useful information and substitute my mixing and prep instructions for what it says on the can. The rolling and tipping and other application techniques will be the same for both paints.


Fairing will take longer and be more of a pain in the ass than any other step in this tutorial. It is also the single most determining factor that separates the men from the boys. Fairing is art. Fairing is science. Fairing is finesse work. Fairing is back-breaking work too. And, in case you missed it the first time, fairing is a colossal pain in the ass.


In a general sense, fairing is incredibly simple; sand the surface, apply fairing compound, sculpt straight lines and fair curves. Easy, right? Wrong.


Lets start with the initial sanding. 80 grit is about right. You want enough “tooth” for the fairing compound to mechanically bond with the surface. Anything coarser than that and you run the risk of severely altering the boat's profile.


The first step is to spray on a guide coat. A quick drying black lacquer spray can is your weapon of choice here. You're not painting the boat black, just a light dusting of paint over everything. When you block sand the boat, the remaining black paint is going to show you where your low spots are.


To sand the boat, you want to use the biggest block available that won't alter the profile. For wide flat areas, take your fairing board and sand widthwise with the board. In other words, if your fairing board is 5” wide and 16” long, sand a path that is 16” wide with each stroke, not 5”. This is the most common mistake I see from DIYs. Overlap every stroke by a few inches, so as not to create sanding grooves.


This photo shows the proper orientation of a fairing board.

Your goal at this stage is to find out where the highs and lows are, not to upbrade 100% of the surface.


Because this boat has been previously painted (dark blue over red gelcoat), not everything in this tutorial is going to be the same. In this particular case, the blue paint acts as the guide coat and, to some degree, as fairing compound.

While the boat will still need some fairing, the thickness of the paint has done much of the work for me.

The foredeck will need the most fairing. Notice that some areas are blue paint, others are red gelcoat, while others are down to bare fiberglass. Proper fairing of the foredeck is going to make this boat look like it just came off the showroom floor.

Initial topside sanding is nearly finished. Tomorrow will bring the first round of fairing compound.

This shows the wobbles, peaks, and valleys of the fore deck. In the photo below, notice the distorted reflection of the toe rail.


In this shot of the Skagit accent color on the hull, everything looks fine.

But using a wet reflection, the yardstick held against the hull shows the hard spot created by the false transom.

Sanding a dark color shows all the flaws in a previous paint job. Here is an area where the accent color on the hull narrows to only several inches. This inaccessibility is probably what lead to poor prep work ultimately leading to the fish eyes seen here. Most likely the result of improper de-waxing the first time around.

When the boat is fully sanded, there will be low areas where the black paint is still visible. Use a pencil to outline these areas then, using a soft block, sand inside the lows until the surface is uniformly upbraded. Take care not to sand your pencil marks away, redraw them if necessary.


The low spots on either side of the red portion in this photo are the result of a previous attempt to sand this area for paint prep without removing the hardware; in this case, the hardtop.

When the boat is 100% sanded, clean up everything. Vacuum the boat, vacuum the floor, vacuum the walls, vacuum your clothes, vacuum your cat... Dust is the enemy. Dust is what weakens the bond between two surfaces. In this case, the boat and fairing compound.


Now solvent wipe the boat...again. Clean up your rags and any other mess and prepare an area for mixing up fairing compound.


Your choice of fairing compounds is as varied as your choice of fillers. You can use a simple polyester-based fairing compound, vinylester, epoxy-based, or a proprietary fairing compound, such as Awl-Fair.


My choice is West Systems epoxy mixed with 410 Microlight fairing filler. I can mix up exactly as much as I need and I can mix it to any desired consistency, (I mix it lighter when fairing vertical bits and fillets to avoid sags). It is stronger than ester-based resins and it adheres tenaciously to gelcoat.


Proprietary fillers (Awl-Fair and others) are guaranteed to be chemically compatible with proprietary primers and top coats. They are strong and cover very well. The problem with any product that begins with the prefix, “Awl-” is the price. I bought a 5 gallon kit, (2 ½ gallons each of a two part compound), of Awl-fair for about $500. It was enough to paint two different boats, (one was 38', the other was 23'), but I just couldn't justify the cost for something that was so task-specific. In the end, I went back to West Systems because, for the same price, I can mix up the same amount of fairing compound and also use it wet out fiberglass, create adhesives, fill gaps, blah, blah, blah, (depending on the filler used).


Side note: If you used thickened epoxy to fill the nicks and dings and gouges earlier, you must use an epoxy-based fairing compound. Polyester and vinylester will not stick to epoxy very well.


Ester-based faring compounds are cheaper than epoxies and proprietary fillers, but are more porous, not as strong, and (polyester) shrinks even more than epoxy. I'm not saying don't use them, I just giving you the facts. The truth is, if this is your first major refinishing job, I recommend vinylester above epoxy and proprietary fairing compounds. You'll probably end up sanding away half of what you put down, which may be throwing money away. Even though it's more expensive than poly, it shrinks less, is more waterproof, and more forgiving than the others (a note about “more forgiving”, because it shrinks less than the others, what is fair today, is more likely to be fair tomorrow than with epoxy or polyester). You will have to make this judgement on your own based on your pocketbook, your motivation, and local availability.


Back to the boat.


When applying fairing compound, you don't want to just butter up the whole boat and then sand it all off. That is what the guide coat is for. Start off at the low spots with thin coats. In between coats, blocksand the way you did earlier and keep using guide coats. You don't want to wast expensive materials and you don't want to waste expensive sandpaper so sneak up on “fair”.


First pass of fairing compound on the fore deck.

...and on the side decks

Second pass of fairing compound being long-boarded off the transom.

The first time you do it, you'll have no idea how much is the right amount. Just use less than you think you'll need. With successive coatings, you'll develop a feel, not only for how much to apply, but how to apply it smoothly. (Yes, you have to sand and solvent wipe the boat between each coat. See, I told you it was a pain in the ass).


If your using vinylester or polyester, your working time is going to be far less than that of epoxy, so mix small batches and don't overwork it. Get it on the boat as smoothly as you can, then learn to walk away.


One of the hardest parts of fairing a boat, in fact, the hardest part, is knowing when to stop. Your eyes will lie to you. Your eyes will see color variations between gelcoat and fairing compound and tell your brain that the two are not level with each other even though it might be perfect. Your hands and fingers have to be your eyes. Feel for variations.


At the end of this never-ending process, use fresh water on the boat and look for imperfections in the reflection. Make sure the boat is clean and dust free when you do it. Get the boat as close to perfect as you can.


The next step is going to make it perfecter.





Side note: When rebuilding the transom, I ground back all 26 holes that had been drilled in it and reglassed them. But I also did something that is an extra preventative measure that you should all consider.

The drain tubes sit below the waterline. While the tubes themselves are generally not damaged by moisture, the wood core material through which they've been installed is almost always the first part of a transom to rot.

To circumvent this eventual source of future headaches, I removed the drain tubes completely, and, when installing the new core material, left a 1" void around the perimeter of the drain tubes.

I then filled that void, (and the drain tube holes themselves), with thickened epoxy, essentially creating a three inch diameter epoxy hockey puck where the drain tubes were, then re-drilled the one inch holed through the epoxy.

Now, if water gets through the bedding compound around the drain tubes, it still won't be able to reach the core without first finding a way through an inch of epoxy in any direction.

This camera is lousy at close up shots, but I think you get the idea.


End of Part One.