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Installing a deck plate is an easy way to gain access to concealed components. Bonus: It’s not as scary as it sounds
Tools
- Drill and bits
- Hole saw
- Jigsaw or rotary saw (for cutting a non-round hole, or if a hole saw is not available)
- Phillips screwdriver
- Pencil
Difficulty
- Easy/moderate
Materials
- Deck plate
- Stainless-steel screws
- Blue painter’s tape
- Marine sealant
- Sandpaper
- Acetone or isopropyl alcohol
- Rags
Time
- 1 to 2 hours
Cost
- Around $50
Most production boats are built in two or three pieces. The hull and stringers are assembled first, at which time plumbing, wiring, fuel system components, and so on are installed in the open hull. From a manufacturing standpoint, this makes a lot of sense as it is easier and more efficient for the boatbuilder to do this work when technicians can install systems without any obstructions, which also helps to keep costs down.
However, once the deck or “liner,” (a one-piece mold usually comprising the deck, inside gunwales, and top cap in a two-piece boat) is dropped onto the hull and fastened, things like thru-hull fittings are often rendered completely inaccessible, meaning when something belowdecks or behind the liner needs attention, it’s necessary to create an access point if the builder didn’t already provide one. This is also the case when installing aftermarket items such as speakers, rod holders, or trolling motors, which require thru-bolting or wiring from beneath the deck.
But fear not, the solution is simple! With the right approach, it’s easy to cut a hole where access is needed and install a deck plate so you can get your hands where they need to be. Deck plates are available in a variety of sizes and styles, with some intended for semipermanent installations, and others offering a pry-off or screw-down lid for easy access. The frequency with which you need access to the area will dictate the best style, as screw-down plates offer better protection against water ingress, while styles that open are preferable for areas that need routine service or inspection.
Regardless of why you need access or what type of plate you choose, stow your anxiety, as installing a deck plate is a simple job that can be done in an hour or two with the right tools. Here’s how to do it right.
The first thing you need to do is choose a suitable location. The location of whatever you need to access will obviously play a big part in this decision. But there are a few things to keep in mind. First, you’ll want a perfectly flat surface to mount the plate to, otherwise it will be challenging to seal it. If possible, identify things like stringers, bulkheads, fuel tanks/lines, and rigging tubes so you’re sure there will be no obstructions where you want to cut. Boatbuilders are often willing to share design schematics that show exactly where things are belowdecks. If that isn’t an option, use a small hammer to tap around, listening and feeling for dead and hollow spots, similar to looking for studs in a wall. Inspection cameras and mirrors can sometimes be useful in these situations.
If you determine that an obstruction does exist, your next step will depend on what you’re trying to accomplish. If installing an aftermarket component, consider an alternate location that will provide a better opportunity for access. For things like speakers and lights, a small shift in location may offer much easier access. If you’re trying to reach an OEM component such as a thru-hull fitting and are not able to cut a simple hole close enough to reach it, you may have to consider a more intrusive action, like removing a portion of the deck, in which case you should consider consulting a professional to do the work.
Bottom line: If you’re uncertain about what may be behind the surface you’re preparing to cut, do not cut.
1. & 2. Prepare the area. Gelcoat is like the hard candy shell on an M&M. It seals the fiberglass beneath from water intrusion and provides a brilliant shine. But it’s also quite brittle and can chip easily. To help avoid chipping the gelcoat, lay blue painter’s tape across the entire area to be cut.
3. Mark the location. Lay the deck plate over the location and trace the diameter of the inside of the flange with a pencil.
4. Drill a pilot hole. Mark the center of the circle and drill a small pilot hole.
5. Select an appropriately sized hole saw and insert the guide bit into the pilot hole.
6. Make the cut. Put the drill in reverse (there’s less gelcoat chipping when running backward) and very slowly begin cutting, stopping as soon as you have made it through the material. Be sure to hold the drill perpendicular to the surface and take it slow to prevent the hole saw from jumping around.
If installing a plate that requires a shape other than a circle, you can use a jigsaw, but it will likely be a more difficult job. If that’s the route you go, drill holes in each corner of the shape to form the radiuses, then use the saw to connect them. If using a conventional blade, select one with a high tooth count. A better alternative is the “grit style” from companies like Remgrit. Instead of teeth, these blades use a hardened abrasive edge, making them great for cutting fiberglass and other hard materials, as they cut more cleanly, resist heat, and last longer than conventional blades.
7. Dry-fit. After successfully cutting your hole, dry-fit the plate to ensure a good fit. Mark the screw holes.
8. Drill pilot holes. If you’ve already removed the tape, put some more where the screw holes will be before drilling. Keep in mind that, unlike wood, fiberglass is very hard, so select a drill bit that is just slightly smaller than the screw diameter to avoid crazing, chipping, or cracking. After drilling the first hole, test the size by using a screwdriver to install a screw. If it binds or is overly tight, expand the hole with the next bit size up, then drill the rest of the holes.
9. Clean it up. With all your holes drilled, remove any remaining tape, and use sandpaper to smooth any rough edges.
10. Prepare the surface. Wipe the surrounding area with acetone or isopropyl alcohol to remove any wax or contaminants.
11. Seal it. Lay a bead of sealant around the perimeter of the back side of the deck plate or frame. As your deck plate will be above the waterline, choose a semipermanent variety, such as 3M 4200 or BoatLife Life Seal so it can be removed easily if needed in the future. Use enough sealant to thoroughly seal the plate and the screw holes, but don’t overdo it; these products can be a mess to clean up.
If the deck plate is located in an area cored with wood or another absorbent material, it is necessary to seal any exposed coring to prevent moisture ingress and, ultimately, delamination. This is commonly done by applying thickened epoxy resin to the inside edge of the hole, and then lightly sanding any rough spots once it has cured. If this step is needed, you may have to cut your hole just slightly oversized to accommodate any resin accumulation.
12. Fasten. Use high-grade stainless-steel screws (SAE 316 is a good choice) to secure the plate. They should be close to the thickness of the material to be fastened to but not long enough to come through the other side. This is to prevent unsealed penetrations that can allow water into any coring and to avoid exposed screw points that can cut you when your hand or arm is in the hole.
If the plate is installed in a liner or area composed of thin fiberglass that doesn’t offer enough thickness for a screw to fasten securely, you can also use machine screws to thru-bolt it. (If this is the case, you will have to use a deck plate style that opens to access the nuts.)
We recommend using a screwdriver for this step instead of a drill so you can easily feel any binding and avoid breaking screws or stripping the pilot holes. Use a star or crisscross diamond pattern when installing the screws, getting all of them in before going back to snug them up.
13. Wipe up. With all the screws tight, wipe away any sealant that was pressed out.
14. Water test. Attach the cover. If using a plate that opens, test for any water intrusion after the sealant has fully cured. Give it a good soaking with a hose, then open it up to see if any water made it in. If it did, check the O-ring on the plate to ensure it is in good condition and not deformed. If everything else looks good, you may want to consider resealing.