Gremlins on Yachts?

What's that crackling, popping sound under the hull?

Those are the gremlins talking about what to torment you with next! Though nobody has ever told me, I believe the sound comes from crustaceans. Barnacles and the sort have some pretty good parties & can't seem to keep the noise down when you're trying to go to sleep.

Where'd that water come from? More often than not, from someplace completely different from where you found it. The gremlins put it there merely to taunt and torture you!

Gremlins loves to eat Chips. So get all the Chips out of your Boat start with the ones in the Electronic Equipment.
If they are gone the Gremlins will get off the Boat.

I believe Carl may have been looking for a mixture of seriousness and fun.

A dangerous "Gremlin" on an older boat, or a boat that is new to you but has older wiring and fittings, is bilge pumps and float (bilge) switches.

An example:

You have a boat with older aft bilge pumps and float switches, probably near to the gearbox area. In the main bilge you should have a larger bilge pump in the deepest part of the bilge/hull and next to it a float or other type of automatic switch.

A distance above this, probably half way up the bilge, typically be another float/auto switch wired to an alarm.

This way if the aft pump/s or float switches fail, then the main bilge will fill, the switch attached to this pump will power up the main bilge pump when the bilge fills and IF this pump or switch fails, then the alarm will be sounded when the bilge fills and lifts the alarm float switch.


This is not an unusual area for water intrusion. All it takes is worn packing around one or both the shafts from the engines and the sea water will come in relatively fast after a short time of running the vessel.

Here is the Gremlin:

At the dock before leaving, being a reasonably good boatman, you check the bilges, through hulls and where the shafts go through the hull. Gremlin has disguised the bad leak from one of the shafts because you have not used the boat for a while and sea growth has filled in the gaps between shaft and hull so that either there is a little bit of water intrusion, as there should be, or none. However, when you get underway, the shafts movement removes this growth and the water starts to enter the bilge at a faster rate.


Now the combination of issues:

Let’s say this is occurring on the Port Side.

The switch or the pump on the AFT Port side fail due to age or electrical issues with old wiring. Badly corroded wiring is common in areas covered in sea water regularly.

The water enters at a faster rate as the spinning port shaft cleans away the growth that had been blocking the opening where the shaft packing has worn and while the boat is underway, the water fills the rear Port bilge.


Then as the skipper slows the boat down, this water rushes to the lowest point in the bilge, forward, to the main bilge. The sudden rush of water fills the main bilge swiftly and because the electrician or previous owner, has wired connections to the main bilge pumps too low in the bilge, or, once again the wiring is old and corroded, the quick water rush shorts out not only the main bilge pump where it is connected to the switches, but also the alarm.

So the owner/skipper, happily ties up his boat and being in a relaxed mood after a SHORT voyage, joins his guests. Meanwhile the bilge fills, with only a third of the Bilge pumps operating.


This scenario easily occurs. A combination of old wiring, poorly positioned and waterproofed connections and, maybe, below average maintenance can result in this occurring.

The owner returns and if he is smart, re-checks the engine room before getting underway, or if he is anchoring, then checks that only his house batteries are on, and sees the bilge full of water!

It can take a while to figure out how this Gremlin worked his way around.

I've had a gremlin on our boat almost since we bought her 5 years ago. The port side batteries never seemed to hold a charge as well as the stbd side. The port engine wouldn't crank over without using the crossover switch. That was the most visible symptom.

My mechanic spent two days down there chasing sparks and trying to find out what was causing the port batts to go down. He thinks he found it--a battery cable on the bow thruster batts was not on properly. Slightly canted on the post and not as tight as it should have been.

He corrected that then let it set for a few hours. Batteries were already starting to show signs of a new outlook on life. After 24 hours the port engine would crank but very slowly. After 36 hours it fired right up. Let's hope that gremlin is dead and buried.

I think it's crustaceans as well. Very small ones and LOTS of them. If you have super clean bottom- as in just painted- I hear less of them than when I have a dirty bottom.

I finally found the answer on a boat I saw today!

On a delivery, I couldn't figure out why I found the bilge full of water each morning. I finally got up the nerve to taste the water - it was fresh! Turned out the popoff valve on top of the water heater was stuck open and the fresh water system pump was emptying the water tank through that valve.