bertram31.com

While removing the rear deck and replacing the fuel tank ,I Thought it would be a good time to fix a leak on the port rudder. This leak wasn't the stuffing box but from around the flange . I removed the 4 bronze bolts that were reduced to half their dia. My question is, do I need to replace the bolts with bronze or is stainless OK? Also what sealant should be used to mount the flange to the hull ? The sealant used was hard and cracked and was 1/8 to 1/4' thick , at first I thought it was a spacer that had cracked but the more I looked at it ,it was the the same stuff used under the old fuel tank. Where can I buy these Bronze bolts?

I vote 316 stainless bolts and 3M 4200, IMHO.

The flange is bronze so if you do use stainless make sure you use teff gel or something along those lines. Otherwise you have two dissimiliar metal under water touching each other.

3M 4200 or Boatlife with bronze bolts from www.boltdepot.com

Silicon bronze is your best bet.

316 SS is the second choice, but I'd gladly pay double and wait a week for the Silicon Bronze

You don't want to use ANY grade of stainless steel in a location where all or part of the metal will be constantly immersed. It will corrode when used under the waterline, even the A316 alloy.

Trust me on this, I thought the same thing about the A316 and learned the hard way, even when all the while the knowledge was out there to be had. Stainless steels need air to form the passive layer that protects it. The name is rather deceiving...

Use only silicon-bronze for any underwater fittings. Jamestown Distributors is a good source I've found for these fasteners, and I'm sure there are others.

No stainless. That dried sealent was Bertrams polyester spacer stuff. Make sure you get things aligned. I would have saved the broken dried stuff for reference.

This is a post under rudder ports you can find on page 2. This was Capt. Pat's response to my question.


Posted: Wed Apr 09, 2008 9:16 pm Post subject:

--------------------------------------------------------------------------------

Tony,

The only ten minutes that I was away from the phone today was when you called... O'Brian's Law

1. Remove the ports. Put a thin coat of petroleum jelly on the flange & tube.

2. Grind the inside fiberglass to fresh material, (no 5200 or other non-fiberglass material)

3. Using heavy Visquine or other plastic sheet material, cut a hole somewhat smaller than the shaft tube & pull it over the tube. Let the tube stretch the visquine for a tight fit.

4. Using a 2" strip of the visquine, tightly wrap the visquine strip around the base of tube about 4 or 5 times. Cut off the excess & use a small piece of tape to secure it.

5. Re-install the port, now masked off with visquine. Nuts only have to be finger tight, no backing plates.

6. Mask off the nuts and bolts with blue tape & mask over that with aluminum foil crushed on.

7. Prime the fiberglass with mixed, but not thickened epoxy. Wipe off all excess epoxy, leaving the area thoroughly coated, but only damp with resin.

8. Mix another batch of epoxy & thicken it with West System high density filler or milled fiberglass. Add about 20% by volume of Cabosil, (fumated silica), to your HD thickener. Bring the mix to the consistency of peanut butter.

9. Pack the void around the shaft tube & level it with the surrounding original fiberglass. Carefully remove the aluminum foil only on the nuts & bolts.

10. Allow the epoxy to setup over night and remove the tape & the ports.

11. Sand the surface flush as necessary.

Br,

Patrick

I wasn't able to find silicon bronze oval head slotted 3/8 -16 3" bolts, would flat head be ok to use? Thanks for all your help

would flat head be ok to use?

Yup!

You can find the oval headed bolts at this web site. They are $7.70 each plus the nuts and washers. They actually call them "strut bolts".

http://www.ccfasteners.com/index.html

Dick

Whats the problem with stainless underwater? My 1986 31Tiara has stainless trim tabs and i removed the strut plates to just beef up the glass under them for good measure and they used stainless bolts there as well. I saw absolutly no signs of bolt failure on them. Also have stainless swim platform stancheons that go below the waterline attached with stainless bolts and no problem there. This boat was neglected before i got it and stayed in the water its whole life in saltwater.

Two dissimilar metals touching one another and immersed in a briny solution can cause a flow of electrons that in most cases will migrate somewhere else. This is called electrolisis. You can have the same effect with a pyrometer which is usually made of alumel and chromel twisted together. These are dissimilar metals and during their contact with hot exhaust gasses, a flow of electrons tells a gauge what the temperature is.

I’ve used stainless on brass and bronze underwater and with no ill affects noticeable because I used something to insulate one from the other. On the other hand, when you don’t use an insulator, the stainless is a more active metal and will slowly deteriorate. Sometimes it is a slow process and sometimes it isn’t. It depends on the salinity of the liquid and whether there is any stray electrons flowing around like in a “hot marina”. Someone once showed me a deteriorated stainless bolt that he took off a boat that was years on the hard. I'm not sure I understand how that can happen,............but.

Personnaly, I'd rather use the silicon bronze.

That’s my story and I’m stickin to it.

Dick