Fixing a pinhole leak in fiberglass

There are sounds you just loathe to hear when on a sailboat—a luffing sail, a screaming carbon monoxide alarm, a whining child (OK, you don’t want to hear that pretty much anywhere.)

Here’s another one: A running bilge pump. Or at least, a bilge pump running when you don’t expect to run.

I know I have some landlubbers who read this blog, so quick explainer: The bilge is the lowest part of the hull of a boat. If there is water in the hull, that’s where it will and should go. Most boats have a pump installed to pump the water overboard so it does not, you know, collect and start sinking your boat.

Anyway, we recently had the bilge pump kick in unexpectedly while we were returning from our two-week cruise of the South Sound. We were motoring back to our home marina in Seattle because we had absolutely no wind and needed to hit the road back to Portland so we could start our big move.

When seeing the light isn’t good

I first heard it running while popping down into the cabin to fix a snack. The showers on our boat drain into the bilge, and that’s usually the only time we hear the bilge pump run. I had taken a shower the day before and couldn’t remember if it ran right after I was done like it usually did.

It seemed odd that it would kick in several hours after the fact. I decided to shrug it off.

About 15-20 minutes later, I heard the bilge pump kick in again while I was in the cockpit. That didn’t seem right at all.

C immediately went down into the cabin and started pulling up the floor board covering the engine and the lowest part of the bilge. He looked to see where water was coming from and saw that clear water was coming in from the back part of the boat (aft).

After pulling up boards covering up access points in the aft cabin, he found a pinhole leak in the stern, just behind the rudder post.

That round circle of light in the middle of the picture? That shouldn’t be there.

C asked me to slow the boat down from 2800 rpms until the stern of the boat lifted up a bit. Once I hit about 2400 rpms, water stopped coming in.

And that’s about all we could do while we were underway.

A temporary fix

We didn’t have time to repair the fiberglass before starting our 2020 summer cruise. So we grabbed some toilet wax at a discount store to patch the hole.

It isn’t pretty, but that brown spot of toilet wax is keeping water out of our boat.

While heading north to the San Juans on another windless day, I took the boat up to 2800 rpms. The bilge pump didn’t kick in so it seems the patch is holding up for now.

The mystery of the stern pinhole

But how did the hole get there in the first place? We think something, likely a rock, stuck to our swim ladder. Once folded down, it dug that little pinhole in the stern.

We are considering putting a rubber stopper on the swim ladder to prevent it from rubbing up against the stern and creating another leak again.

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