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Date: 13 January 2022. Thru-Hull Leak Series.


INFORMATION FOUND: Perhaps a decade ago I remember reading the results of a Mechanical Engineers review. They wanted to ascertain what best separated corroded metals. Various products tested including WD-40, PB Blaster, among many others. The winner was a simple 50/50 (half and half) formula containing ATF (Automobile Transmission Fluid) and Acetone. Thank you to Island Time, Rob and Cap'n Mike for letting me know that Acetone was the other half of the formula.

This boater's nightmare became a multi-part series. This page, the Thru-Hull Leak Series contains all articles published regarding the leaking thru-hull fiasco. For those on slower connections or who prefer smaller pieces, the shorter articles can be found here:

Side Note: If I am able to return to the sailboat in question, I will update. For now, this is everything I know. Thank you.

Date: 11 January 2022. Finding the Leak (part 1)

It was a bad day a couple canals south of here recently. Life lessons were reinforced. One neighbor owns an older production sailboat. He experienced the nightmare of water intrusion. Locating where the problem originated was the first priority. Here is what was done.

Like responsible boaters, the owner checks his vessel regularly. He had pumped the bilge dry the previous afternoon. The following morning water was up once again. There was obviously a leak however locating same was the problem of the moment.


This is the ideal...


Though the sailboat pictured on  the right appears similar to the one featured in the (Joshua Slocum's) Spray replica Anja article, they are two different vessels.

Nobody wants to become this boat:

Sunken schooner



The first order of business when taking on
water is to locate where the water is coming in.

Due to a recent injury the boat owner enlisted the assistance of my neighbor who invited me to ride along. Fortunately the sailboat in need was just a couple canals away.

Upon arrival our emphasis was in finding where the problem originated. Wanting to know if the water was fresh or salt, I did the finger in water/taste test. There probably is a better method however mine offered the fastest results.



When the vessel is in salt water, this is
what a taste of bilge water will tell you:


Fresh:  the issue is in the water tank or hoses inside the vessel.

Side Note: Though a lot of people swear that attaching to pressurized dock water is fine, I am old enough to believe this is a rapid way to sink your boat.

Salt water: indicates water was coming from outside the hull, and thus a MUCH more serious problem.


The bilge water was definitely salty. Because the transom is higher than the keel on this sailboat, I opted to start aft. Lifting hatches and checking, we noted zero water. This eliminated one area of the bilge.

Next the main bilge hatch was opened. That is when we saw water:

A THRU-HULL cover had blown. At some point an inferior cap had been installed.

Most of us have utilized a temporary repair at some point or another. The problem with this is that too many folks do not return and properly finish the job. That temporary cap/cover was installed years ago when closing off a thru-hull without a valve. Galvanized steel does not last forever.

The unit had rusted out from the inside. When it finally broke fortunately the stream of water was discovered before it became even larger. That the entire end did not fail is indeed fortunate.

A wise boater checks the bilges every day.

Tomorrow I will share with you the initial part of the resolution for this leak. Thank you for reading.

Date: 12 January 2022. Temporary Thru-Hull Fix (part 2)

The THRU-HULL is shooting water into the bilge.

To recap, a sailboat a couple canals over from me had a thru-hull cap failure. Thanks to that trite term "thinking outside the (wine) box" the problem with the leaking thru-hull was temporarily resolved. Definite emphasis should be placed on the word "TEMPORARILY" as this is in no way a solution, however...!

A quick trip back to Seaweed ensued. I picked up a spare roll of Rescue Tape:



For the first time in over a decade, my Rescue Tape failed me. Although I tried I could not get the tape to stick to itself and entirely seal off the leak.

RESCUE TAPE Self-Fusing Silicone Tape (1", Clear)

I have used the tape successfully to
seal a large intake hose on a workboat.


Affiliate link


In the meantime, like all "interesting" boat projects, the bilge pump failed while we were pumping out the vessel. Yes, it was that kind of day. Fortunately the owner was sharp. He had a spare Johnson 2k bilge pump in his arsenal of spare parts.


Johnson bilge pumps, the orange ones, are rated at either 2000 or 2200 gallons per hour. They come with a five year warranty. I had one fail on me at the six year mark. The other failed at 13 years. All in all, I am impressed. These are good "serious" bilge pumps.

Aboard my 23' long boat, I have two Johnson's plus one 800gph SeaSense bilge pump. The SeaSense is my primary.

Johnson Pump Heavy Duty Bilge Pump

(affiliate links provided: SeaSense and Johnson)


I replaced the Johnson We still had a steady stream of water coming from the thru-hull.

At some point during the fiasco I attempted to seal the end with wax, then the Rescue Tape. That failed too. There is a lot of water pressure 4' (120 cm) deep, which is where this thru-hull intake is located.

We needed to seal off an oddly shaped pipe fitting. At this point we dared not wrench off that cap/cover  for fear of breaking the thru-hull. After pondering I came up with a solution. A quick trip back over to my Seaweed ensued so I could pick up a wine bottle cap/cover.

A couple years back I bought one blue silicone cap from eBay. I had intended to use
it for a project. The Project List aboard Seaweed would be impressive if it were not so scary!

These covers/caps are silicone, approximately 1/8" (3mm) thick. Mine appeared sturdy enough to be utilized as a temporary solution. First I stretched the silicone cover up and over the nipple. Then I added a hose clamp and tightened it.

I did not exert super-human strength. Over-tightening might damage the threads and/or break something.  All due care must be employed so the final repair can be seamless, and easy. Hopefully!

The wine bottle BOTTLE CAP is secured to the thru-hull fitting with a hose clamp.
The boys are calling it a thru-hull condom. Older boatmen are a hoot. They have no filter.


Most important of all, the leak has been stopped. We have bought time with the
simple use of a silicone wine bottle cap.  This is definitely a temporary solution.



Lessons Learned:

  • #1. Check your bilges regularly. In this case had the owner not caught the problem in the initial stages of failure this could have been catastrophic.

  • #2. Check if the bilge water is fresh or salty. A quick taste test can determine if the water in the bilges is coming from the water tanks, or outside the boat. This presumes your vessel is in salt water.

  • #3. Obviously STOP the water. Though we could not get off the galvanized part immediately, we were able to prevent more water from coming into the boat. The unconventional (silicone wine bottle cap) solution is, at best, TEMPORARY. It will need to be carefully monitored until the real repair is completed.


MOST IMPORTANT OF ALL, remember that temporary fixes are just that: an interim measure to buy time. They will fail. That snafu definitely will not be at a convenient stress free time.


The sailboat owner was smart. He checked his bilges regularly. Because of that he recognized there was a problem before it became more serious. Additionally, he had boating friends nearby. Together we were able to temporarily find a solution until that galvanized fitting can be removed and replaced with something suitable.

INFORMATION FOUND: Perhaps a decade ago I remember reading the results of a Mechanical Engineers review. They wanted to ascertain what best separated corroded metals. Various products tested including WD-40, PB Blaster, among many others. The winner was a simple 50/50 (half and half) formula containing ATF (Automobile Transmission Fluid) and Acetone. Thank you to Island Time, Rob and Cap'n Mike for letting me know that Acetone was the other half of the formula.


That is life in bilges. If I may be so bold, you might consider purchasing a silicone bottle cap for your boat too. Fortunately mine was in my silverware drawer, and thus easy to locate. I paid $1 for one from eBay a couple years back.

Side Note: Before anyone reminds me of the wooden plugs for thru-hulls, please remember those will not work in all circumstances. This time the threaded part of the galvanized cap was firmly stuck. Only a stream of water 3/16" (5mm) was coming out of the middle so a plug would be much too large.


For full details on how to get the best prices on eBay, you might wish to read the Screening My Hatch (eBay advice) article. Or search eBay for "Silicone bottle caps cover". Once the results load, chose the option "Sort by Price plus Shipping, Lowest First" ... Thanks!


So that is life on the west coast. If the owner calls my neighbor/me back, I will follow-up with the permanent resolution. In the meantime, remember that Galvanized stuff rusts. It really is awful in a salty environment.

Do not use galvanized gear on your boat.
Signed, an opinionated Stainless Steel gal. :)

Thank you for reading.

I'd love to hear your tricks for removing a galvanized cap from a bronze thru-hull.
And, is there anything you would not do re the galvanized problem?

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Categories: Gear, In the Bilges,

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