Brass Drain Tube Repair

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Brass Drain Tube Repair

Postby jimh » Tue May 07, 2019 3:32 pm

Below are several images that originally were provided as hyperlinks by user "Derf" in a thread on the old forum. These images were hosted on a photo-image hosting site that since then has become unscrupulous and now prevents viewing the images without distracting pop-up advertisements and other surrounding advertisements. I have rescued the images from the hellish experience of trying to see them on the rogue photo-hosting site, and present them here, with some exposure adjustments and with captions based on the original narrative. More advice and suggestions about the installation of a replacement brass drain tube, see the FAQ answer on this topic.

Fig. 1. An old brass drain after being removed using ViceGrips pliers.

Fig. 2. A new tube and the tube flaring tool. This demonstrates a problem with the tool:
the threaded bolt shown is not long enough to use with many drains that will be found
on the Boston Whaler boats. A threaded rod will replace the bolt.

Fig. 3. The new tube has been installed in the existing drain hole. The threaded rod extends
and awaits the forming tool to be installed. The unformed tubing has been carefully cut
to length to provide the proper amount of excess length to work well with the flare
and to match the angle of the tube with the hull surface. The black material is not a
sealant but a lubricant ("PAM cooking spray") to help fit the brass tube into the
existing hole. Do not forget to install the O-rings before proceeding further. The amount
the tube extends out of the hull is about 1/4-inch to perhaps 5/16-inch, and this will be
turned to flare over the O-ring.

Fig. 4. The forming tool is installed and is being tightened in place. In this instance the new
drain is being installed in an anchor locker.

Fig. 5. A finished brass tube end nicely rolled and sealed over the O-ring.

A link to this thread has been added to the FAQ answer to Q12: "How Are Drain Tubes Replaced"? Read the FAQ answer to learn more about installation of brass drain tubes.

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Phil T
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Re: Brass Drain Tube Repair

Postby Phil T » Wed May 08, 2019 7:06 am

The standard 1" flaring tool is widely available. Note prices vary considerably. Below is a link to a good source and good price.

It is important to note you will need to replace the bolt with a threaded rod for some drains. Threaded rod material is available at most hardware stores.
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Re: Brass Drain Tube Repair

Postby rtk » Wed May 08, 2019 9:19 am

This is very timely information for me- I need to replace a few of the drain tubes on my 16 and 21 Whalers. Thank you.


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Re: Brass Drain Tube Repair

Postby dtmackey » Wed May 08, 2019 10:35 pm

I was at my local boatyard today making a work list for one of my boats, and the yard has a bunch of 13-foot Boston Whaler boats from various years scattered about. I checked and found three that had at least one compromised drain tube where the brass was corroded to the point of allowing saltwater to contact the foam and possibly the wood transom core. I cannot stress enough that this should be a yearly check for any Whaler owner, especially in saltwater.

In a perfect world the fix would be to hog out the area behind the gelcoat and fiberglass, fill with resin, re-drill to the size of the drain tube, and then install. This would serve as a barrier around the brass tube in case of corrosion failure, but this is not an easy modification; so follow the instructions offered on this site. As an added measure, I used a bead of 3M4200 sealant around the drain tube lip over the O-ring.

Not all [brass] drain tubes are crated equal. Over the years I've purchased direct from Whaler and from aftermarket sources, and I found that some aftermarket [brass] tubes have a much thinner wall thickness, and the brass appears different in color--which leads me to question if the alloy content of the metal is the same and will last as long.

Just sharing my experience in saltwater. I would expect the drain tubes to last far longer in freshwater.


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Re: Brass Drain Tube Repair

Postby jimh » Tue May 14, 2019 4:37 pm

Regarding the method by which the ductility of brass can be increased by annealing, there are many opinions. A reasonable assessment of this process provides the following insights.

A Wikipedia article on annealing describes the fundamental process:

Wikipedia wrote:Annealing, in metallurgy and materials science, is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for a suitable amount of time, and then cooling.

There are three elements involved:
  1. temperature to which the brass must be heated,
  2. the duration of the heated period, and
  3. the cooling process.

The Wikipedia remarks about brass as follows:

Wikipedia wrote:In the [case] of...brass, this process is performed by heating the material (generally until glowing) for a while and then slowly letting it cool...brass can be cooled slowly in air, or quickly by quenching in water

Unfortunately, this advice does not provide guidance on the exact temperature to which brass should be heated or the duration of time the brass should be held at that temperature. The cooling process is described sufficiently to allow duplication.

A website focused on brass as used in the cartridges of firearm ammunition also comments on temperature and duration needed to properly anneal brass: wrote:Brass is annealed by a certain temperature for a certain amount of time. The higher the annealing temperature, the shorter the time required to anneal. The grain structure of the brass begins to change, indicating the start of annealing, at just under 500-degrees-Fahrenheit. At 600-degrees-F, brass will anneal in one hour. At 800-degrees-F, brass will take only a few seconds to anneal.

Now we have some specific advice on temperature and time.

Regarding the quenching or cooling process for brass after being heated for annealing, two methods are described: a slow cooling in still air or a very rapid cooling by immersion in cold water. I can find no source that suggests only one of these methods will work and the other is inappropriate.

There may be a preference for a particular method when brass is being used in a particular application. For example, in the situation where a brass cartridge for firearm ammunition is being prepared for reloading, the fast quenching method is generally suggested. This may be due to a desire to prevent parts of the brass ammunition cartridge other than the area at the top of the cartridge from being softened by the annealing process; only the top of the cartridge needs to be softened to allow it to be re-formed in the re-loading.

Inasmuch as brass drain tubes on Boston Whaler boats won't be filled with black powder, ignited, and then contain an explosion which will propel a lead or steel bullet at extremely high speed outward from the cartridge, I am not certain I see the advice for rapid quenching of brass ammunition cartridges to have much transference to the preparation of through-hull drain tubes.

If you are impatient and certain that the temperature you have heated the brass to and the time it has remained at that temperature are sufficient for annealing, then you can rapidly cool the brass workpiece. On the other hand allowing the brass to remain at a high temperature for an hour or so while it cools in still air may be a good way to insure that the material was hot enough for long enough to produce the desired increase in ductility.

If anyone reading this is a working metallurgist and has background in the annealing of brass, their opinion on the optimum temperature for heating, the time duration of the heating, and the method for cooling would be most welcome.

As I mentioned at the outset, by searching the web one can find a variety of opinions on this topic offered by people with a variety of backgrounds in the subject. To infer that only one of those opinions is accurate and authoritative is beyond my qualifications to judge.

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Re: Brass Drain Tube Repair

Postby Acseatsri » Tue May 14, 2019 11:12 pm

Re annealing brass drain tubes for flaring: I've found that the rapid quench method works well, is quick, and is easy. I heat the very end of the brass tube with a propane torch until the brass gets a little redness. Then I drop the brass tube in a bucket of water.

I absolutely recommend annealing if you are using.032 wall brass tubing. While changing brass tube drains in 13, 15, and 17-foot Boston Whaler boats in the last month, if I forgot to anneal an end, the brass tube was very hard to roll over at the end. If annealing is done right, you can roll the brass tube half-round to really capture the O-ring.

On angled tube ends as in an anchor locker, grinding away some of the lead on the flaring tool to allow it to find the angle may be necessary.

If you have an air chisel, use it with the flaring tool to preform the first end. I cut off an old chisel and just let the shank of the chisel push on the hole in the flaring tool. This is how I do all brass tube drain replacements now.

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Re: Brass Drain Tube Repair

Postby HenryOHornet17 » Tue Apr 27, 2021 2:09 pm

Before you use a new [flaring or forming] tool, use jeweler’s rouge and a buffing wheel on the working surfaces of the tool to smooth and polish the curved working faces of the tool.

When conforming a brass drain tube to the shape of the forming tool, apply lubricating oil on the working face of the tool to allow the brass to slide.

After cutting the tube to length, use a spherical tool to start the flaring of the cut end. Do not flare the tube end too far or the tube will not be able to be fit in place in the drain passage. Note that cutting the tube usually leaves the cut edge turned inward a little. I use the ball end of a ball peen hammer to just slightly turn out that cut edge.

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Re: Brass Drain Tube Repair

Postby joemahoney79 » Thu May 13, 2021 7:37 am

How is the lower drain tube on a c.1988 13-foot boat flared?

I went through quite a bit of brass stock trying to install one. It is complicated by the angled cut on the outside of the transom and the recessed splash well on the inside. Both don't allow you to use a conventional threaded flaring tool. I tried the pneumatic impact gun setup as well but am not happy with the results.

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Re: Brass Drain Tube Repair

Postby jimh » Thu May 13, 2021 7:59 am

If the inboard end of the drain is location in an area with limited access, AND the tube can be inserted from that end, pre-form the flare on that end of the tube before inserting the tube. Surely at the transom end the access won't be encumbered.

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Re: Brass Drain Tube Repair

Postby joemahoney79 » Thu May 13, 2021 8:31 am

Thanks for the prompt reply. The tube cannot be installed from the inside out because of the recessed low point well so there is no way to preform the inner flare first. They essentially need to be formed simultaneously which is complicated by the angle of the outside flare. I may be missing something simple. Wish I had a window into how the factory does it.

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Re: Brass Drain Tube Repair

Postby jimh » Thu May 13, 2021 9:08 am

Perhaps this method might be useful in the situation you described
  • cut the brass tube several inches longer than necessary
  • insert the tube into the existing hole from the outboard side of the transom
  • insert the flaring tool
  • flare both ends
  • assuming the inboard end has been nicely flared, now cut off the outboard end of the tube to the necessary length and angle to fit, discarding the outboard end of the tube that was flared in the first pass
  • set up the flaring tool, perhaps using a shim on the already-flared inboard end so the tool won't add to that flare and the angle is best for the outboard end
  • tighten the tool and flare the outboard end

I have not tried this, but it might be a solution to having to make both ends flare simultaneously.

Another thought: perhaps the threaded rod used for the flaring tool could be bent slightly to help accommodate the different angles at each end. As long as the bent threaded rod can pass through the ID of the brass tube, a slight bent in the rod might produce a better angle for the flare at one end. The threaded rod could be held at the proper orientation during tightening so it does not rotate and change the angle.

Fig. 6. Sketch showing concept of using a slightly bent threaded rod for the flare tool to enable better alignment of angles when used on sections that are not co-planar.
bentRodFlareTool.jpg (7.89 KiB) Viewed 3969 times

Note that inserting the bent rod should not be difficult as long as the bend is located near the end of the hole used for entry into the brass tube. A threaded rod could also be made with a hinge connection so that any angle variation could be accommodated.