You’ve found the perfect classic boat … or what appeared at first glance to be perfect. It’s the right year and model, and is even the color you’re looking for. But after having searched for this particular boat, you find that its condition isn’t exactly ready for prime time. It’s in tough shape, and you know it.
 
Once the hook has been set, you’ll probably go ahead with the purchase of your dream boat, no matter what. But you have some serious decisions to make: Will the dream deteriorate into a forlorn-looking mess out behind the garage, or will a plan of action deliver your project to the water in style by the next boating season? If you’re buying the boat, you need to make a commitment to the project, setting some ground rules and hopefully a timeline for the boat’s repair or full restoration.
   
There are times, of course, when the best thing to do is turn the job over to a professional. But for many of us, having the work done by others is out of the question. In terms of cost, we’d really prefer to do it ourselves — and perhaps learn some new skills and gain the rewards associated with bringing the old boat back to life with our own two hands. Two of the most common problems found on neglected classic fiberglass boats are weak transoms and rotten plywood floors. There may be lots of other issues, but these are the most critical elements — and not beyond your ability to repair, if approached carefully.
These structural repairs can be done at home, but remember that if you attempt this kind of work, you become responsible for the integrity and strength of the boat. If something structural is removed — especially a transom — something of equal or greater strength must take its place.
 
While you may not give floors a second thought, they’re integral parts of the structure of most boats, working in close conjunction with stringers between the floor and bottom of the hull, or with the keel itself. Either way, floors are an important piece of your boat’s backbone, giving the hull its maximum strength. Again, transom and floor repairs can be left to professionals, but you can probably accomplish these tasks on your own. Here are some things you need to learn, or consider: 

What To Look For

The first thing you need to do is evaluate the condition of the floor and transom. Floors are usually easy to check: If it feels solid under your foot when you stomp on it, it probably is. But if the plywood is rotten or delaminated, you’ll notice softness in spots or separations of the floor from the underlying stringers or keel. Transoms can be trickier. Almost all transoms in fiberglass boats from the 1950s and 1960s were made of plywood, sandwiched just inside the hull’s thin fiberglass skin. Usually, but not always, the plywood transom is also covered on the inside by a layer of fiberglass matting, which means you may not be able to easily inspect the plywood. So, how do you know if the inner ply core has problems? The first clue will usually be a bowing-out of the transom in the center area, under the long-term weight of an outboard motor, indicating weakness or rot in the plywood core. Rotting in transoms starts either at the bottom, where bilge water has seeped into the wood; at the top, if the plywood’s upper edge has been exposed to water; or sometimes in center areas, when transom through- hull bolts haven’t been adequately sealed from outside moisture.
 
If you can’t easily detect rot, but you suspect the transom is weak, there are a few ways to sleuth out the soft spots. First, gently tap the transom with a small hammer or wooden mallet, moving slowly across from side to side and top to bottom. Where the transom is solid, you should hear a crisp, consistent "bonk," and the hammer should bounce back at you. If the tone changes in one spot, or in a whole area — from a lively "bonk" to something resembling a dull "thud" — you may have found rot, or at least delaminated plywood that’s lost strength. If tapping on the hull doesn’t tell you enough, you might want to drill core samples — literally boring 1/2-inch holes into suspicious areas of the transom. Either the wood that curls out on the drill bit will be dry and fresh-looking, or it will be a dark and moist pulp, indicating rotten plywood.

Demolition Time

Once you’ve determined the floor or transom have problems, you need to begin surgery. It’s fairly easy with the floor, since some floors are so bad you can literally peel them out of the boat after getting a grip along an edge near the transom or sides of the hull. If it’s not that easy, you’ll want to bring out your main surgical tool — the circular saw. If you don’t know the exact thickness of the floor, begin by setting your blade at 1/2 inch and make a cut across any section of the floor that needs to be removed. If you’v e been able to cut through the floor on the first pass, just make your way around the perimeter until you can lift the entire floor out, in one piece or in sections. If you weren’t able to pierce through with the blade set at 1/2-inch, adjust it to 5/8-inch. Try again. If you need to go deeper, just work your way toward 3/4-inch, which should be deep enough to cut through most runabout floors. You don’t want to go any
  deeper than necessary, in order to avoid cutting through stringers, or worse, though the bottom of the hull. With transoms, if you can determine the rot is confined to just one area, cut out only portions that are actually rotten or delaminated. Rot is often confined to just lower portions, or only upper sections. In such cases, try to make a straight cut from side to side, leaving as much good wood as possible. If you’re using a circular saw to cut into the transom on the inside, be sure not to cut through the outside fiberglass shell of the hull, since the outer casing is critical to the hull’s integrity. You’ll probably find you can come close to the outer skin, making horizontal and vertical cuts until you’re able to pry or chisel out smaller sections of weak or rotten plywood. In the end, you’ll most likely be working with only a sharp chisel and hammer or mallet, cutting all remaining fragments of soft ply out of the boat, making sure you get down to nothing but nice, healthy plywood.

Replacing the floor    

Once you’ve successfully removed the floor and transom (or portions thereof), and you’ve cleaned up and dried out the mess, you can start the rebuilding process. If you’ve found rotten or broken stringers under the old floor, you’ll need to begin by replacing the bad ones. If you’re lucky, you’ll be able to use the old ones as blueprints. If you’re not so fortunate, the task of shaping replacements, fitting and glassing them to the inside bottom of the hull becomes a more tedious process. Let’s assume the floor is the only part needing replacement, since that’s usually the case. Following removal of the old floor, or a section of floor, you can often make a good pattern for the new piece(s) by simply measuring the opening, assuming it’s a neat rectangle or trapezoid. Once you have the dimensions, you might want to "prove" the shape before cutting into an expensive new sheet of marine or exterior-grade plywood, by instead using cheap 3mm doorskin or 4x8 sheets of cardboard — just to be sure the measured shape fits the opening. Once  you’ve cut the new sections of floor and they fit tightly in the space, you’ll want to thoroughly seal both sides of the replacement panel with either a one-part toluene wood sealer or two-part clear penetrating epoxy sealer (CPES) before screwing and epoxying the pieces onto subfloor stringers. If sections of your new floor lie adjacent to old flooring in-between stringers, where there’s no support for the new flooring, you’l l want to epoxy butt blocks along the undersides of the old floor, so the new plywood has something to land on. This will give the new floor more strength between stringers and increase its longevity. After screwing and gluing the new sections of floor in place, you’ll have to overlay the work with a 6-ounce, resin-saturated fiberglass cloth to give the floor more strength, durability and water-tightness.
 
Filling the void 

A final step you might want to consider, when replacing rotten floors, is to fill all voids under your new floor with floatation foam. You can buy two-part closed-cell foam kits (not to be confused with the spray foam for household insulation) from companies specializing in fiberglass and epoxy products such as Fiberlay (www.fiberlay.com). When you mix Part A with an equal portion of Part B, the magic happens. The epoxy expands to more than 30 times its liquid volume, filling all cavities with foam that cannot be penetrated by bilge water. Filling all sub-floor areas with floatation foam will make your boat virtually unsinkable in the event of an accident, and will also add stiffness and sound insulation to your new floor, giving you a quieter ride on the water. When you pour the thoroughly stirred A and B portions from your foam kit, you need to give the foam some elbow room. It’s going to expand rapidly and with
considerable force, so you have to give it a few escape routes to ensure it doesn’t expand by lifting your new floor skyward. We use 1 1/2-inch vent holes between each row of stringers, at 16-inch centers fore and aft. By tipping the hull up during your foam-pouring adventure, and by starting at the low point and working uphill, you’re able to completely fill all voids under the floor. At the same time, you’ll give the expanding foam an escape valve when it overflows.

Transom Work 

Most of the procedures described for floors also apply when you’re replacing transoms, or sections of transoms. After test-fitting your pattern, cut and fit the new layers of plywood, then seal all wood surfaces, especially the edge grain of plywood, before epoxying the sections of new transom in place. All of this is pretty straightforward if your old transom is completely flat. But if there is any pronounced curve to the transom (viewed from above), you may need to build up your new transom with several layers of thinner ply, bending, clamping,  gluing and screwing each successive layer into place. The way to start is with the layer that butts against the fiberglass skin of the hull, but how do you securely hold the replacement panel tight against the curving surface of a 15- to 25-inch deep transom? Assuming you don’t own a collection of giant, long-armed woodworking  clamps, one solution (here you must show bravery) is simply to drill small pilot holes all across the outer face of your boat, 10 inches or so apart from one another, sinking dozens of No. 12 by 3/4-inch panhead screws, backed with 3/4-inch washers, right through the outer transom layer and into the epoxy-gooped first layer of new plywood. You may need a friend to apply pressure to the plywood from the inside, while you run screws in from the outside. This is often the best or only way to make sure the new wood makes full contact with the hull’s outer skin, which is important to the longevity of your new transom. When the epoxy has cured, simply back out the panhead screws and fill the pilot holes with a sandable two-part filler such as Evercoat Lite.
Additional layers of new transom plywood can then be epoxied and screwed onto the previous layers from the inside, until your new transom has reached the desired thickness. While most runabout transoms from the 1950s were only 1 to 1 1/2-inches thick, your objective should be to make the new transom stronger than ever — ideally 2 to 2 1/4-inches, with the exact thickness determined by the plywood used. I like to go with three layers of 3/4-inch plywood for flat transoms, four layers of 1/2-inch ply for slightly curved transoms, or six layers of 3/8-inch ply when you’ve got to deal with some real curves.

When you fit and attach the new sections of transom plywood, you’ll no doubt have gaps around the bottom and side edges of the new ply. Not a problem — just mix some two-part epoxy, and thicken it to a peanut butter consistency
by adding silica power (available at marine supply stores), and trowel the thickened goo into all voids. You want it thick enough that it will not run or sag when worked into the crevices. Ideally, you’ll have time to use the angled edge
of a paper cup to trowel in a nice smooth radius, maybe 1 1/2-inches in diameter, where the new transom meets the sides and bottom of the hull. Once the epoxy fillet has cured, slather on some fiberglass resin and apply 6 ounces of fiberglass cloth, using 3-inch fiberglass tape to cover the corner joints and larger precut sheets to lay over the rest of the new transom upper lip. You may need to use more glass-cloth tape, 2 to 3 inches wide, to wrap over the upper edge of the transom. Just be sure you make it watertight, since you don’t want to repeat this act five years from now.

Other Details

Some of the processes described may have to be altered for your boat, depending on its design. For instance, if the boat had transom knees in the past, they’ll perhaps need to be removed to easily install the new floor and transom. If you remove old transom knees, you’ll want to replace them with stronger ones, perhaps larger in size, and better adhered to the transom and bottom. A lot of 1950s boats had no transom knee or only a small one down the centerline. There’s nothing to prevent you from rebuilding the boat better than when it came from the factory, so feel free to use two knees instead of one, or beefier under-floor stringers than the broken, split and/or rotten stringers you’re pulling out of the boat. Remember, these were simple production boats in their time, never intended to be in use half a century later.

Finishing Up

Once your construction work is done, and you’ve sanded the new transom and floor sections smooth, you may want to fill any remaining hollows, fiberglass-tape edges or other voids with more of the sandable fiberglass filler, such as Evercoat Lite. After everything is smooth, use a good two-part primer such as Interlux Primekote, and finish with a one-part polyurethane paint, such as Interlux Brightside or Pettit Easypoxy, or Interlux’s two-part Perfection paint. You can brush these paints, or use the roll-and-tip method. This requires working with a partner. One person rolls paint onto the hull using a thin-nap, yellow-foam "weenie" roller in a horizontal pattern. The other person follows behind with a semi-dry bristle brush, gently brushing the rolled-on paint smooth, using top-to-bottom vertical strokes. You can reverse the pattern on successive coats if you wish. You can also spray the paint, but that’s another article unto itself.

Considering Gelcoat

You may ask, "Well, don’t I need to use gelcoat to make my boat look original, since it had a gelcoat finish at the factory?" The short answer is no, don’t bother. Gelcoats are harder to use and more expensive than most paints. And when cured, they don’t immediately look glossy and beautiful; they’re dull and ugly, until you’ve applied tons of elbow grease tediously rubbing out the gelcoat, finally developing the gloss you’re looking for. Modern urethane or polyurethane paints can give you an appearance just like gelcoat in a fraction of the time and for less money, so keep the whole job as simple as possible, while obtaining results that look absolutely professional.

Marty Loken specializes in the restoration of classic fiberglass boats together with vintage wooden boats, and he’ll be happy to help you, if possible. If you run into trouble and need advice, just take digital photos — if they’ll help explain the problem — and e-mail your questions to Marty@islandboatshop.com. If you’re not an avid e-mailer, send queries to Marty Loken, c/o Island Boatshop, P.O. Box 216, Nordland, WA 98358.