Propeller Shaft Cooling Water Fitting

[BigEasy]

Has anyone replaced the 3/8 inch brass fitting that supplies cooling water to the propeller shaft? The fitting is threaded on one end and has a barbed hose fitting on the other end. It is bonded into the fiberglass shaft log.

How did you remove the old fitting? How did you install the new fitting?
How often do you replace it? In my research, I have not been able to locate a bronze fitting of the same size. My boat is now 7 years old, I don't think that the previous owner replaced it. I inspected it about 14 months ago on haulout; however, I am a bit concerned about it and plan to replace it next month.

 

[Captn TJ]

Big easy

This has been an extended thread on the 423 yahoo group site. There have been a number of fixes too numerous to mention. However regardless of the fix care must be taken not to damage the prop shaft since there is little clearance between the fitting and the shaft. Suggest you join that group or a different model for solutions.

 

[BigEasy]

Just wondering if a marelon fitting would be a better alternative for the prop shaft cooling water fitting. Seems that marelon would be better than using brass that is subject to galvanic & saltwater corrosion. Have not been able to locate a 3/8" bronze fitting anywhere and evidently no one else has either. Seems that Beneteau is now advising placing a 3/8" brass fitting and using 3M 5200 to bed the NPT end of the fitting into the shaft log instead of "special" epoxy as installed at the factory. Would epoxy affect marelon in a harmful manner? Would 3M 5200 adequately bond marelon to the shaft log? Just considering options here. I certainly don't like the idea of using brass in a corrosive environment.

 

[Captn TJ]

Big easy

There have been two issues with 423 fittings. The first is deterioration of the fitting itself - appears to be mostly salt water related. The second is the thin wall of the shaft tube (at least on the 423). The latter has led to the fitting snapping off. If your boat has the same wall thickness it would probably preclude you using a marlon fitting. In any case the most successful repair on 423's has been a heavy build up of glass mat and epoxy with a new fitting. An alternative approach has been installing a PSS Dripless shaft seal. Then sealing up the prop shaft hole for the old fitting.

My recommendation is a heavy Fiberglas build up and a new fitting.

 

[BigEasy]

Captn,
Makes sense to beef up the thickness of the shaft tube to engage more threads on the fitting. Still have concerns about using brass in saltwater environment. After modification to make the shaft tube thicker, do you think that a marelon fitting would be a better alternative than replacing with a brass fitting?

 

[Captn TJ]

Personally I would prefer metal over marelon. I've never seen marlon below the waterline

At some point today or tomorrow I'll download a photo of the built up solution for you

 

[Captn TJ]

Personally I would prefer metal over marelon. I've never seen marlon below the waterline At some point today or tomorrow I'll download a photo of the built up solution for you

Here is a link to one of the 423's that have improved the fitting with a build up. There are a number of photos but two of them pertain to your situation

http://groups.yahoo.com/group/Benet...de=tn&order=ordinal&start=21&count=20&dir=asc

 

[Fred Villiard]

McMaster has some stainless fittings, and maybe bronze, that might work for you.

 

[Ron20324]

For those who have already suffered this failing, would it do any good to build up the area NOW, before it fails? Or, is the failure the barb itslef, or just the physical thread connection. Like, I'm wondering if bedding the barb in 5200 or epoxy or whatever, would keep the connection intact?.

 

[BigEasy]

Captn,
Thanks for the advice & photo. I agree with you that building up the tube appears the easiest, cheapest, & most effective solution. Plan to do this on haulout in March. I would still like to investigate using marelon vs brass. There are some individuals who use marelon thru hull fittings, marelon ball valves, and marelon tail piece fittings instead of bronze. Cost is certainly a factor for an entire thru hull & valve assembly as marelon fittings are more expensive. Cost of a marelon 3/8" barbed fitting for the stern tube is insignificant. However, I would want to make sure that the fitting has significant strength. I would think that if the tube was built up with FG to sufficient thickness to engage all of the marelon threads & tapped to 3/8", the marelon could then be "screwed" into the fiberglass tube and sealed with 3M 4200. That repair method would allow the fitting to be "unscrewed" in future
for replacement or inspection. (instead of using epoxy to bed the fitting to the shaft tube.
I believe that such a repair would solve both failure problems: (1) the brass fitting failing due to galvanic corrosion & saltwater exposure (2) the brass fitting snapping off because of insufficient threads engaging in the thin fiberglass shaft tube. HOWEVER, I certainly don't want to use marelon if it isn't sufficiently strong.

 

[BigEasy]

Fred,
Thanks for the suggestion. Will try McMaster. Would be great if I could find a 3/8 fitting in bronze; however, have not been able to locate one yet. I would be reluctant to use a stainless fitting without knowing what alloy it is as some stainless alloys (430,304,410) actually have more galvanic corrosion potential than brass. A passive grade of stainless would be great if I could find it. Also wonder if "crevice corrosion" would be a potential problem in this application.

 

[BigEasy]

Ron,
My understanding is that there are two failure mechanisms:
(1) failure from severe galvanic corrosion or corrosion from exposure to seawater. (2) failure due to the brass fitting snapping off of the shaft tube because only a few threads are engaged on thin tube. (Can't screw in completely because it will bind on shaft inside the tube. Obviously, the installation from the factory seems to work with the brass fitting epoxied into the shaft tube with a generous amount of epoxy "outside" the shaft tube , helping to bond the nonengaged threads to the exterior of the tube. I don't like the idea of simply bonding a new fitting to the thin shaft tube with 5200 because of the limited thread engagement . I don't think that 5200 on the outside of the shaft tube would lend any support whatsoever. Even with the installation from the factory, corrosion is a factor and that is why it is recommended to change out the fitting every two years or so. I definitely like Captn TJ's idea of building up the exterior of the shaft tube with additional fiber glass to provide a thicker / more robust area to completely engage the threads of the fitting. Just not sure of what material would be optimal for the application; bronze (can't locate source), passive stainless steel (don't know if it is available), marelon, or brass. I am not comfortable at all using brass because of its high potential for galvanic corrosion. Makes me want to assemble an emergency kit with wide diameter rubber hose and extra large hose clamps to clamp around the hole in the stern tube if the fitting ever corrodes off or breaks---may not be able to get a wooden plug in such a small hole.

 

[Captn TJ]

Bigeasy

Let us know how you make out - especially if you use marelon.

 

[DougM]

Thinking about this for awhile, there is another possible way to deal with this. Could a nut be epoxied to the outside of the shaft log over the existing hole? With that, a fitting could be threaded into it providing more thread engagement. It seems like that would make the system a bit stronger. That might allow the use of the original fitting if it hasn't already been snapped off. The whole design is vulnerable. Somehow inserting a fitting into the side of the shaft log would be less vulnerable than the entire valve assembly pointing vertically.

I really wonder what the existing fitting is made of. I would imagine bronze is going to be difficult to find. Maybe Beneteau parts has them, or could provide a source.

 

[Captn TJ]

Doug

Along the same lines you can cut a stainless tube , thread it and fiberglass it in.

 

[BigEasy]

Captn TJ,
Thanks for the recommendation to visit the 423 site. Wow, there was a wealth of information there. I like the idea of building up the thickness of the tube with mat & resin to enable complete engagement of the fitting threads. I ordered a 316SS barbed fitting from McMaster and will tap 3/8" NPT threads into the FG. Haven't decided on using 3M4200 to seal threads, permatex, or Teflon tape and Real Tuff paste thread sealant. I would like to be able to easily remove the fitting for inspection / replacement every 18 to 24 months on haulout without difficulty. Will also order a marelon fitting and check it out. After reading all the posts on the 423 site, I am nervous about the darn thing breaking off ordisintegrating since it has been in for 6 years; one month to go before haulout! Thanks again for the photos & resources.

 

[BigEasy]

Doug,
I have been in touch with Beneteau and they advise buying a 3/8" Brass fitting from a hardware store and bedding it with 3M 5200. According to other sources, Beneteau doesn't even sell the fittings any longer! Needless to say, I don't like the idea of placing another brass fitting with minimal thread engagement into the shaft tube and relying on 5200 to keep it in place. Your idea to glass in a nut above the hole in the fiberglass shaft tube would certainly beef up the strength of the assembly. As of now, I plan to follow Captn TJ's recommendation to buildup the thickness of the tube with mat & resin and retap to 3/8"NPT. Plan to use a 316 SS fitting or marelon.

 

[Gunni]

When I checked my shaft log fitting a couple of years ago (per Beneteau) I found a pipe firmly epoxied into the shaft log. Removing it to inspect was a ridiculous notion because I was clearly going to destroy the area around the threaded nipple if I did so.

What I did was remove the hose, inspect the brass fitting interior for signs of corrosion (there was none), and resolve that I will replace the entire ridiculous affair with a PSS slip ring seal while the boat is on the hard, and I can back out the shaft. I will remove the nipple, and glass over the hole.

If you attempt to do remove the brass nipple with the shaft in place how can you know that you have removed all the bits of fiberglass, and epoxy that will fall into the shaft log where they will collect, clog the cutlass bearing water channels and generally make a mess of the whole system. The current system works, but it is a dumb design. I will not replace it. In the mean time, I have a small bung tied to the nipple.

 

[BigEasy]

Gunni,
Last time I hauled out, I did the same. Cut the rubber hose off of the brass fitting & checked for corrosion. Tapped on it with a hammer and all checked out well. I don't want to push my luck any further. The fitting has been in for 6 years, time to change it and while I am at it I want to modify so that it will be a more trustworthy installation and also to simplify removal & replacement in future.
With regards to bits of glass falling into the shaft log, I intend to vacuum while removing the brass fitting and vacuum while drilling new hole & tapping threads. If there is any indication that shavings have fallen into the shaft log, I intend to remove the cutlass bearing and flush it out with water.

 

[Ron20324]

Have not been able to locate a 3/8" bronze fitting anywhere and evidently no one else has either. .

I was just at Fawcetts in Annapolis, and they have bronze hose barbs. I didn't recall where or what size you needed. 800-456-9151, 410-267-8681 www.fawcettboat.com . Their GW sale is ongoing.