Rot Repair in Fiberglass Boats

Outboard Transom Repair
Most of the older outboards have relatively simple center-section access. You remove the top and there you are. The risers on each side can present a problem if the rot has gotten that far. If so, more often than not you'll be in for some serious fiberglass cutting. Remember though, if you cut carefully and save the pieces they can often be replaced with an epoxy filler as a bonding/filling substance.

A. Let's take a look at a standard repair:

1)  Remove transom top, and (as many as possible) fixtures attached to the transom. Tape the holes shut.
2)  Dig out bad wood with a hook-like tool (i.e. a caulker's reefing iron or a sharpened and bent file.
3)  Allow interior to dry, or blow-dry. Drill a small water outlet hole at the bottom of the transom. (You can fill it later with Epoxy Filler.) Clean out or vacuum out loose debris.
4)  Treat the gutted area and surrounding wood with CPES™.  Just pour or spray on the CPES™. Keep doing that until you see CPES™ starting to dribble out the hole you drilled at the bottom of the transom. You can capture it and re-apply if you wish.

IMPORTANT: to prevent recurring rot, all wood in the surrounding area (even if it is not rotted) needs to be treated with CPES™ as well. The rot fungi are there. You can use a spray or a swab but you must get the CPES™ on the wood.

	5)  Allow about a week for the CPES™ carrier solvents to evaporate away and the epoxy to cure. After this, close the hole you drilled in the bottom of the transom. Our Fill-It™ epoxy filler will do this quite well. 6)  Measure, cut, glue (if required), and CPES™ treat the replacement wood. This can approximate the size, because you're going to fill around it with a resin-mix.
	7)  Drop the wood into position and fill around with a flowable mix of Layup & Laminating Resin™ and sawdust. The sawdust can be quite coarse. Make sure that the mix flows well before pouring in place. 8) Allow 24 hours for preliminary cure.
	9) Close off the top with either a putty made from the sawdust and L&L Resin™ or with our Fill-It™ epoxy filler. 10) Replace the top on the transom. Re-drill motor mount holes. Bed everything back in place. Remember what we said above about bedding compounds: Don't use silicone and make the process a two-step procedure. If you get into the side risers you are basically repeating the above process. It can be done in stages if necessary.

The method above was used by one of our customers to repair their transom. We feel that it was a very well planned and executed repair, and as the process was well documented, we thought that you might like to see the results. The following link is to a copy of the web pages that he put online, and was kind enough to let us incorporate into our site. To view the repair job, click here.

VARIATION: On some boats it is possible to get at the transom from the inside. There are advantages to this method; for one, it would not scar or deface the outside of the transom. Simply cut away the inner face of the transom, save the glass piece if possible, and tear away the bad wood. Treat any wood left inside with CPES™. Cut new wood and treat with CPES™ and insert into transom, clamp/epoxy-glue it to the back of the transom, fill in all gaps with either the Fill-It™ epoxy filler or a putty-mix of the L&L Resin™, and then re-glass the inside. It's real work.

Another customer sent us a brief description and pictures of his transom repair as well. He accessed the bad wood from the inside of the boat. While not as detailed as the repair above, you may find the pictures informative. To take a look, click here.

UPDATE: After 2 years, the original repair repair mentioned above is still going strong according to the customer. If you want to read his report and see the pictures, please go here.

AN EASIER ALTERNATIVE...
The easiest method of repairing transom rot is through drilled holes (much like deck repair), but the results are far less certain. It can work well enough, though, particularly in situations where there is adequate time for the transom interior to thoroughly dry.

Drill 1/4" holes across the top of the transom, about 5 to 7 inches apart and allow the interior to air dry. Drill a drain hole at the bottom. After the interior is dry, inject the CPES™ into the holes, recapture excess at the drain hole, and re-inject.   Allow at least two weeks for the CPES™ carrier solvents to evaporate away. Close the bottom drain hole with Fill-It™ epoxy filler. Using a turkey baster, flow pure mixed Layup and Laminating Resin™ into the holes. Keep applying it until the holes will accept no more. Let cure 24 hours. Close the holes with Fill-It™ epoxy filler. Sand smooth and apply a water-barrier paint.

Inboard/Outboard Transom Repair
Most often the rot in I/O transoms is right around the mounting bracket openings. Again, its a matter of hooking out the bad wood until you get to the good wood. If the rot goes further than you can reach, then you're going to have to get at the transom wood from the top (review this procedure in the "Outboard Transom Repair" section). As we mentioned, this can be a total hassle but what can we say? Cut carefully, save the pieces, and then re-install with epoxy filler.

Getting new wood into areas that is above the mounting holes will involve bedding it in our Fill-It™ epoxy filler (after CPES™ treatment, of course) and propping it in place for 24 hours until the filler cures. If you wish you can fill overhead space entirely with the Fill-It™ epoxy filler. This may take two applications to get a smooth final fill. For awkward areas, the CPES™ can be sprayed on or injected into the wood, allowing the wood to absorb as much of the liquid as it can. It is essential that the face of any wood not replaced be thoroughly soaked with CPES™.

When finished re-drill bracket holes and bed everything down.

Note: We have had customers who have cut away exterior transom glass to get at the rotted wood inside, and they have done this without removing the outdrives and mounting brackets. After the repair, the glass panels are bonded back in place with Layup & Laminating Epoxy Resin™ and the cut grooves filled with Fill-It™ epoxy filler, the surface sanded and then painted with a polyurethane paint. It can be done.

Floor Replacement

One of the most common areas of damage on fiberglass and pontoon boats is  deteriorated or rotted-out cockpit/deck flooring. The reasons are obvious: water saturation through leaking glass laminate and plywood. Sometimes this can be repaired by treating the existing wood or by drilling access holes in the glass laminate and injecting CPES™ (Clear Penetrating Epoxy Sealer) and, if the damage is severe, Layup & Laminating Resin. We cover this process under Deck Repair in a later section.

Often, however, it is easier and more thorough just to pull up the old floor and replace it with new wood. This also will give you a look at the flooring sub-structure, the fore/aft stringers and the supporting cross beams. Sometimes they require repair as well, and we do cover this process under Stringer Repair in a later section.

When making the floor replacement, there are some special considerations regarding type of wood and its treatment before the wood is installed. The object is to give you a new floor that will withstand future water saturation without rotting out again.

Treatment of the New Wood
After the wood is cut, trimmed, drilled and ready to install, it needs to be treated to prevent deterioration and delamination. The product of choice here is CPES™ (Clear Penetrating Epoxy Sealer). The CPES™ will penetrate deeply, especially on cut edges, and prevent the wood from absorbing enough moisture to support fungal and bacterial activity. We recommend at least two generous coatings on all cut edges, and three coatings is better. The flat bottom of the sections should receive two coatings, and the top one coating. All drilled screw/bolt holes should also be treated with CPES™, and if you are applying self-tapping screws a puddle of CPES™ should be put on the wood before the screw is drilled in. The threads will drag the CPES™ into the wood as they penetrate. On new wood you can figure coverage will be about 250 sq. ft. per gallon of CPES™.

Installation of the New Flooring
How you install the new flooring will depend on the structure of the hull or floats and what you have torn away. If you are going to bond the new flooring to the hull, then use only epoxy resin, such as our Layup & Laminating Resin, and 'glass tape. Polyester resin will not bond well with epoxied surfaces, and is not nearly as strong as epoxy.

Engine Beds and Mounts Engine beds and mounts can be a problem on older glass boats. Running hours alone tend to shake things loose, and then add a little water to soften things up and the engine starts hopping around. Here is a typical inboard engine installation for a shaft drive. It is the usual 4-point mount onto a steel frame over wood beds. Other mounting configurations are shown below. The photograph shows a typical I/O mount with steel pedestals through-bolted on a chopper-glassed wood beam. Click on image for larger view.

Engine Mount Repair When the Wood Is Accessible
The wood is usually integral to the mounting system; if it goes bad then things shake loose. Repair will depend on the extent of the damage. If the wood is totally shot then it should be replaced. This can be a hassle because you've got to pull the engine. Just as often the damage is a matter of stripped-out mounting hole wood that has gone soft. This can sometimes be repaired with the engine in place, or the engine can be jacked up and skidded over to give access to the hole. Repair is then usually a matter of cleaning out the hole (drilling or chiseling), saturating the newly exposed good wood with CPES™, inserting new wood which has also been CPES treated, and then embedding the new wood in Layup & Laminating™ Epoxy Resin. After this you re-drill the mounting hole, treat it with CPES, and then fasten the engine back down. You may have to do a bit of re-glassing as well, being sure to use epoxy resin, not polyester.

And you might as well repair all the mounting holes as long as you are involved in the process. If one is bad then the others are likely not in great shape either.

For the above process to work the wood must be reasonably dry and oil-free. (Wood with oil on it should be drilled or chiseled away.) Blow the holes with a hair dryer for a few hours before proceeding with the CPES. Allow at least 3 days to pass after the CPES treatment for the carrier solvents to evaporate away before proceeding with the wood and L&L Resin rebuild. After that 48 hours between steps is sufficient.

One way or another the repair process outlined above will work on just about any wood/steel engine mount configuration where the wood is accessible.

Basically this forms a very strong plug inside the stringer to hold the engine securely in place. It doesn't solve the whole stringer problem, but much of the stringer strength is in the fiberglass “hat-section” formed by the stringer itself. The fiberglass on some stringers approaches 1/4” in thickness, in which case the wood interior is almost redundant.

It's important in these kinds of repairs to use our Layup & Laminating Resin, because it has a slower setting (time to settle) and because it will never shatter or crack under loads. In hot weather these repairs should be made at the coolest part of the day, since heat accelerates the cure time of all polymer resins. And don't even think about using the standard polyester resins. They set too quickly, are brittle, and not sufficiently strong for an engine mount lag/bolt.

Don't skimp on resin use! We realize that epoxy resins are expensive, but it takes an adequate amount to create the solid base for your engine lags/bolts to attach to. Just remember that the resin is a lot less expensive than paying someone to remove the engine, cut the tops off the stringers, replace the wood, re-glass the stringers, and then re-install and line-up the engine.

Here is a step-by-step outline of the repair procedure:
1) Remove the existing bolts/lag bolts that hold down the engine. You might want to check them all while you're going through this procedure.

2) Remove any aluminum plates or other items have been added to improve the structure.

3) Take a stiff hooked wire (such as a bent coat hanger) and probe around inside the mount hole. Any soft wood should be broken up and shop-vac'ed out of the hole. It will also give you a rough idea of the amount of Layup& Laminating™ Epoxy Resin you will need. You can estimate the cubed inches of interior vacancy and then convert cubic inches into fluid ounces, and then fluid ounces into pints/quarts/gallons.

4) Give the areas a few days (or longer) to dry out, that is, vent away moisture that may be trapped inside the stringer fiberglass laminate. Compressed air can also be used to dry wood quickly.

5) Using our injection kit or ketchup dispenser or something similar, squirt the inside of the stringer with our CPES (Clear Penetrating Epoxy Sealer). This will harden any remaining soft wood, and it will help eliminate all fungi/bacteria in the wood. You'll need about 1/2 to 1 pint of the mixed CPES per mounting hole, depending on the size of the stringer.

6) Wait for a few days while the CPES gasses-off the carrier solvents.

7) Now, if there is any wood remaining inside the stringer fiberglass laminate, pour in slowly our mixed Layup & Laminating Resin. This will gradually be absorbed by the wood and will make it very hard. You will need about 1/2 to 1 pint of the L&L Resin per mounting hole. If there isn't any wood inside the fiberglass, then you'll proceed directly to Step # 8.

8) Mix our Layup & Laminating Resin, add some of our fine sawdust until you get a fairly thick but still pourable mix. Pour or pump (see our Reusable Caulking Tubes) it into the mounting hole. If you have first put in the pure L&L Resin (Step # 7) and there is still space inside the hole, then add the L&L Resin/sawdust to those mounting holes as well. Pour/pump in as much of the resin/sawdust as the mounting hole will take in about 1/2 hour period of time. You'll probably use anywhere from a pint to a quart of the resin/sawdust per mounting hole, depending on the amount of empty space.

9) After 24 hours the resin/sawdust will have cured. You should be able to see it in the hole. Come back now and mix a thicker mix of the L&L Resin/sawdust and using our re-useable caulking tubes pump or pack it down into the hole until it backs up against the poured mix. Level off at the surface.

10) Drill new lag bolt holes in the resin/sawdust mix, and screw in the lags.

Wood-Cored Decks

Rot and general wood deterioration in cored decks is a particularly difficult problem, largely because it's so hard to get at. We hear more about it in sailboats than power boats, probably because sailboats have more hardware sticking through their decks (and therefore more locations for the water to get in), and because they are often driven harder in worse weather conditions than power boats. Below is a general diagram section of a sailboat showing the cored decks and cabin top. What this doesn't show are the sail tracks, chain plates, stanchion bases, winches, cleats and so forth that are poorly bedded or work loose and allow the water into the wood interior. Believe me, the water is bound to get in. The wise skipper will apply CPES™ generously to every hole whenever a screw or bolt is removed. You'll never completely keep the water out but you can treat the wood so it's nothing that fungi or bacteria will want to eat when rot conditions become a factor. The diagrams below show a small and large power boat with wood-cored decks.

Click on pictures for close-up view.

Decks are most often cored with plywood or end grain balsa. Occasionally foam or a plastic core system is used, but usually not. The diagram shows some typical cores, and a couple of photographs of a power boat deck showing the wood core.

Once the deck or cabin core decomposition becomes severe you'll know it: Things get a bit springy up there. Mild decomposition may not be so evident, but can be detected by pulling bolts/screws and inspecting the holes, or by tapping the deck and listening for tonal differences. If there a lot of air under there, it sounds hollow. You can also test drill through the deck to take a look. More often than not you'll be right so the test hole is no issue. If the wood turns out to be good, squirt it with some CPES™ and then after the CPES™ cures fill in with an epoxy filler. Our Fill-It™ dries just off white and smoothes nicely.

• Plan and mark your cut wisely. Plan a cut with future restoration in mind. Use straight lines. Consider placement of non skid overlays and deck fittings.


• Set cut depth to glass thickness only.


• It may be necessary to work skin free from core with the edge of a putty knife; apply heat to loosen further if needed.


• Try to remove the skin intact. It can be reapplied over the new core.

• Outline the damaged area with straight lines and using a paper pattern transfer this outline to the inner skin. Line up exactly by measuring from permanent deck fittings or bolts.



• Drill an exploratory hole to determine how far the underside of the outer skin is from the surface of the inner skin. Fit a circular saw with a carbide-tipped plywood bit and set the cutting depth to slightly less to allow for some variation in this dimension. Cut around the outline.



• Finish the cut through the core with a razor knife. If the top skin bond is completely broken, the cutout will drop out. If not, find a loose corner and pry down, then use a sharpened flexible putty knife as a chisel to free the rest of the core. Heat applied to the outer skin may help.

• Chisel the damaged core from the inner skin or use a utility knife (for balsa or foam), or a saw (for plywood). Carefully and thoroughly clear the inner skin of any old core material.



• Make a paper pattern of the empty section to cut new material.



• NOTE: it is important to use core material the same as the original, both in type and thickness. The exception to this would be the plastic honeycomb core material--which can be mixed with other types. It should be the same thickness, however.



• Dry-fit the core into the cavity, trimming as necessary.



• Wet out the surface of the old core and skin where the new core will bond with CPES™. Allow 1-2 days for CPES™ carrier solvents to evaporate.



• Wet out all bonding surfaces, both new and old with Layup & Laminating Epoxy Resin™ thickened with talcum powder or colloidal silica to the consistency of mayonnaise, and put new core in place. Brace or weight the core in position, and allow to it to cure.



• Wet the old and new core with CPES™ and allow 1-2 days to cure.

Delamination

Delamination: Decks and Cabins
Occasionally decks and cabin sides will delaminate from the core. The core itself is okay, but the glass is popped up on top. You need to drill the perimeter and treat with epoxy. Here is a schematic.

We recommend the use of our Layup & Laminating Resin™ because it is a simple 1:1 mix, very slow setting which allows the epoxy to settle into position and retain a slight flexibility after curing. For filling holes, our Fill-It™ Epoxy Filler goes in neatly on top of the epoxy, smoothes cleanly, dries in 24 hours, and can then be easily gel-coated or painted.

If there is wood involved and you suspect deterioration or rot, you can apply CPES™ first to the holes, but this will mean waiting for at least a week for the carrier solvents to evaporate away. Then the Layup & Laminating Resin can be applied.

Delamination: Hull Blisters
Blisters on the hull bottom are common on some boats. Water (especially salt water) gets under the gelcoat and into the laminate and bad chemistry results. The laminate is compromised, and unless repaired the blisters will get worse. On the other hand, we've never heard of a fiberglass boat sinking because of delamination blisters. No need to panic, but it does give the mind something to think about.

Vast arrays of blisters is a boatyard job. Few owners will have the time to make the repair themselves. Everything has to be ground down, dried out, and built back up with epoxy. Big job... takes time... costs money.

A few blisters are repairable by the owner, but it will take a little time. Pop them open, clean away the gunk, clean the opening area so it's free and clear, and dry out the laminate. If you've got a long time (say 6 months or more) they will eventually air-dry, or you can vacuum dry them, or you can apply blowing warm air, as from a hair dryer. It will still take time - you gotta be sure things are dry. The ordinary moisture meter won't be much help. There are specialized ones that will work, but they are expensive.

Dry until you are sure it's dry inside. Clean out with our Epoxy Solvent or xylene. Then apply CPES™ to the area, allowing it to wick in as much as it will. Allow 2-3 days to go by, and then apply another coat of CPES™. Allow 2 days to pass. Then another coat of CPES™, one day dry time, and then another CPES™ application. You can do this as long as you want, allowing a day dry time between applications, because what you are doing is building thin layers of epoxy in, on and around the glass matrix. No other epoxy product you can buy will penetrate these very small spaces as well as CPES™. A single 2-pint unit of CPES™ will carry you through a whole bunch of blisters. From this point on you can apply a thick resin coat or go directly to a filler, such as our Fill-It™ Epoxy Filler. Push it in, smooth it off, and paint with an epoxy or polyurethane barrier-coat paint. The repair will be virtually waterproof.