Seal The Deal

Hatch replacement

or rebedding made easy

By Frank Lanier   Photos by Craig Harlamoff

With the possible exception of Karaoke night at your marina’s Tiki Bar, nothing can ruin a good night’s sleep quicker than hitting the V-berth after a day of boating only to find soggy bedding due to a leaky deck hatch. Hatch leaks can also cause major structural damage over time if left unchecked. Maybe the hatch simply needs to be pulled and re-bedded (caulked) or perhaps it’s damaged and you want to upgrade to a more robust unit, one with a more modern look to it. Even if your existing hatch is serviceable, parts for older, discontinued hatches are often hard to come by should the need for repairs arise.
Regardless of the reason, with a little planning and preparation, pulling a hatch for repair or replacement is a project well within the ability of most any boat owner. Here are some tips on how to do it right.

Many owners choose the same solution to repair a leaky hatch—throw lots of sealant at the problem as seen in the above two photos. This rarely works as a long-term solution. At right, note the corrosion on the boltholes in the hatch. If rebedding this hatch, the corrosion must be thoroughly cleaned off.

Why hatches leak
Although hatch leaks can be caused by damage or component failure (cracked lens, worn or inoperative dogs, missing gaskets, etc.) one common cause is failure of the sealant between the frame and deck.  Boats are not totally ridged structures and even well constructed ones twist and flex, working and eventually breaking the caulking seal. Although larger breaks mean more leaking, even minute failure points in the caulking can pull in water due to the capillary effect.
As a marine surveyor I often see caulking gobbed around the outside edge of a leaky hatch in a futile attempt to stem the flow of water, an approach that’s slightly less effective than throwing sawdust against a waterfall (and lot messier looking). Once seal failure occurs, the only real option is to pull and re-bed the hatch.

Hatch pulling basics
While hatches may differ in size and style, the basic steps for removal and reinstallation are pretty much the same for all.
A good quality hatch installation will be secured with nuts and bolts, typically in an arrangement that sandwiches the deck between the flange of the hatch frame and an interior trim ring.  Screws are also commonly used by builders to mount hatches—not because they’re better— but cheaper and quicker to install.
Although dealing with screw mounted hatches is a fact of life for many boat owners, screws are a horrible way to fasten anything to fiberglass, a brittle material that doesn’t provide good holding. This is particularly true if the fastener itself will be under a load or flexing.

Pull the old hatch
This can be a relatively simple affair or a battle of epic proportions, depending on the condition and type of sealant used to bed the hatch. If the caulking is in poor condition, the hatch may pull out fairly easily, however the more likely scenario will involve a bit of persuasion using a flexible putty knife to help cut the caulking. If the hatch was installed using polyurethane adhesive, one of the spray on de-bonding agents such as Anti-Bond 2015 may help.

Clean and inspect
Once the hatch is pulled, the next step is to remove the old caulking and clean all mating surfaces of the hatch and fiberglass deck thoroughly with a suitable solvent (acetone works well, assuming you have a metal hatch).  This step can’t be stressed enough – failure to remove ALL of the old caulking will guarantee the new installation will leak.  If there’s oxidation or corrosion on the hatch flange, you’ll need to remove that as well.

Dry fitting the hatch
Once the hatch and deck are cleaned, dry-fit the hatch to make sure everything fits properly.  Five minutes here can save you five hours labor later on.
Rules for successful bedding
• Apply plenty of sealant. When tightened, caulking should squeeze out all around the hatch frame flange. If it doesn’t, you’ll likely have to do it over to ensure a watertight fit. Excess silicone can be trimmed away with a razor blade once cured. For polysulfide and polyurethane caulks, apply masking tape around the outside of the flange prior to bedding, then smooth out the caulking with a moistened finger and peel the tape promptly, leaving a clean edge.
•  Tighten the mounting hardware until the caulking begins to ooze out around the flange, but not enough to squeeze out all of the caulking. The objective is to snug the hatch down enough to bed it while leaving enough caulking to form a gasket once cured. If done properly, you will still have the option to tighten it down a bit more in future.
•  Snug-up the hardware after the caulking has completely cured (typically a couple of days) to place the seal under compression.

Tune in next month, when we discuss that using that Aqua-sling you got for Christmas to lob a couple of jumbo water balloons into the Tiki Bar next Karaoke night can actually help cure insomnia…