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-   -   General Info: When to replace thru hulls?? (https://www.cruisersforum.com/forums/f139/when-to-replace-thru-hulls-100247.html)

timbenner 18-03-2013 17:59

When to replace thru hulls??
 
I have a 2002, 380, on the hard, finishing up a refit. How do I know if I should replace the thru hulls?? Any testing advise?? Are the thru hulls like rigging and should be replaced every "X" years??

Tim

osirissail 18-03-2013 18:25

Re: When to replace thru hulls??
 
Well, first things first - the "Through hull" is the screw-in fittings that passes through the hull and into the "seacock." Which is the valve that allows you to keep the ocean on the outside of the hull.

Then there is the matter of whether your "Seacock/Through-hull" combination are made of metal (e.g. bronze) or resin (e.g., Marelon - or God forbid PVC).

Typically, bronze or actually any Seacock material gets "sticky" and unless lubricated and exercised become very difficult to open and close. So a schedule of lubrication and exercise (opening and closing) them is important. If they have never or rarely ever been lubricated or exercised then they might become "frozen" and you cannot open/close them without risking breaking them. In that case, replacing them would be advisable. Or at least removing or disassembling them to clean and refurbish makes sense.

Otherwise, if they are functional and not broken, cracked or otherwise compromised there would be no reason to replace them. However, if the Seacock/Through-hull is bronze it is possible that it has been subject to stray electrical currents and "de-zincified" which turns the normal bronze colored metal "pink." Then it would also be advisable to change them and correct the stray electrical problems.

Just like screws, Through-hulls come in different head styles - mushroom/round head or flush/flat head. Sometimes if the boat has been run down some hard dock or other obstructions the mushroom/round head style Through-hull can get the portion that is on the outside surface of the hull, scrapped off or broken. Then again it would be advisable to install new ones.

Also if the Seacock is not a tabbed base "flanged" style which is bolted to the hull and instead is merely being held in place by the threads of the Through-hull, it would be advisable to remove the Through-hull and check it for cracks in the threaded section. However, since the Through-hull portion is normally "bedded" with adhesive caulk is it rarely possible to remove it without breaking or destroying the fitting. So if there is no indication of any leakage leaving the system alone also makes sense.

So there are several variables to consider as to whether "replacing" them is advisable or not. More important sometimes is to check the hoses attached to the Seacock and the hose clamps and their condition as the hose clamps rust and break or the hoses dry out and get rigid and fracture or crack.

timbenner 19-03-2013 09:59

Re: When to replace thru hulls??
 
Osiris,

Thanks for the input. I think I've got factory bronze thru hulls on a Lagoon 380. I'm thinking Titanium, so I never have to worry about them again. Hose Clamps from Titan are 100 Percent Titanium

sailorboy1 19-03-2013 10:10

Re: When to replace thru hulls??
 
Quote:

Originally Posted by timbenner (Post 1189193)
Osiris,

Thanks for the input. I think I've got factory bronze thru hulls on a Lagoon 380. I'm thinking Titanium, so I never have to worry about them again. Hose Clamps from Titan are 100 Percent Titanium

If you think that the "normal" 316SS clamps are not enough then I think you have a bigger issue! The titanium clamps probably aren't as strong, but it doesn't really matter.


As mentioned I would be more concerned about the thru fittings than the valves. On my last boat I went to replace a frozen 3/4" valve, only to find out the 2-1/4" thru fitting on the valve next to it had completely corroded away and the largest hole in the boat was being held together by caulking (a stray current issue)!

This is thread drift, but that experience also let to my being in the don't bond sea fittings to the boats electrical circuits. I my opinion connecting things that aren't suppose to have current going though them to something that does is asking for a problem.

timbenner 19-03-2013 10:17

Re: When to replace thru hulls??
 
They claim that Titanium is 40% stronger and 40% lighter than Stainless Steel. I gave you the wrong link to titanium thru hulls. Here's the correct one: Thru-Hulls - Titanium

timbenner 19-03-2013 10:18

Re: When to replace thru hulls??
 
Titanium looks like the best long term solution. The cost of titanium is competitive as well.

Cheechako 19-03-2013 10:28

Re: When to replace thru hulls??
 
If you dont mind being a Beta test go for it. I tend to stick with proven products for safety items. Not that I dont respect Titanium's corrosion resistance, but it can be pretty crack prone if not properly engineered. I dont think a 2002 boat should need it's bronze seacocks replaced though, unless they are showing defects.
Bronze 3/4"= $14
Titanium = $60
You probably have bronze thru hulls with ball valves screwed onto the stems? I wonder what the combo of Bronze and Ti does to the bronze...?

boatpoker 19-03-2013 10:43

Re: When to replace thru hulls??
 
Every Lagoon I have seen has chrome plated NPT brass ball valves on NPS bronze throughulls (In no way can this arrangement be called a "seacock"). A UK Marine Surveyor has several articles on this issue which some consider very serious particularly in salt water. Compass Marine also has some terrific articles on this issue and both sites have some great photos of potential problems.

sailvayu 19-03-2013 11:17

Re: When to replace thru hulls??
 
I agree with boatpoker the French boats use a poor quality brass. It is CE approved but I would not have it on my boat. Also laggons use ball valves on thru hulls not a proper seacock with flange. I would replace them all with proper seacock like those made by Apollo, Combraco, Buck Algonquin, or Groco. I have had lagoon fittings crumble in my hand while working on them they were so corroded.

careka 19-03-2013 13:51

Re: When to replace thru hulls??
 
Lubricate ?? with what, ?? oil, ?? or. Seacocks. ball valves,

osirissail 19-03-2013 14:53

Re: When to replace thru hulls??
 
1 Attachment(s)
I wouldn't get all that excited about "titanium" hose clamps or though-hulls fittings. First off, the Titan hose clamps are "perforated" bands. That is a mark of an inferior hose clamp. The 316SS AWAB clamps are, IMHO, the best since they are made 316SS parts and used indented threading. See photo below. AWAB Hose Clamps

The problem with perforated hose clamps is that rust or stress fractures develop in the very narrow edge of the clamp strap. Then they break regardless of the metal used to make hose clamp band.

As to using titanium through-hull fittings - more than likely you will be using bronze seacocks or whatever and whenever you have two dissimilar metals connected together in the presence of salt water - here comes electrolysis and rapid deterioration of the less noble metal.

If indeed the Lagoon used ball valves mounted on the stems of through-hull fittings, I would agree with removing them and replacing with flanged base seacocks and matching through-hull fittings. Using flanged base seacocks that are bolted to the hull removes all the stress on the through-hull fitting along with eliminating the problem of breakage if somebody or something heavy falls on the seacock/valve.

And I would agree with the others that standard quality brand name seacocks and through-hull fittings are perfectly fine and there are probably better areas to spend "extra" money than going with exotic metal fittings.

offline 19-03-2013 14:56

Re: When to replace thru hulls??
 
Quote:

Originally Posted by careka (Post 1189404)
Lubricate ?? with what, ?? oil, ?? or. Seacocks. ball valves,

I believe that common practice on any boat is to lubricate anything that needs maintenance with large quantities of whatever cash is on hand. :devil:

Cheechako 19-03-2013 16:11

Re: When to replace thru hulls??
 
Quote:

Originally Posted by sailvayu (Post 1189278)
I agree with boatpoker the French boats use a poor quality brass. It is CE approved but I would not have it on my boat. Also laggons use ball valves on thru hulls not a proper seacock with flange. I would replace them all with proper seacock like those made by Apollo, Combraco, Buck Algonquin, or Groco. I have had lagoon fittings crumble in my hand while working on them they were so corroded.

:thumb: This is good advice, concentrate on replacing with a proper flanged seacock as a higher priority rather than exotic alloys.

"I wouldn't get all that excited about "titanium" hose clamps or though-hulls fittings. First off, the Titan hose clamps are "perforated" bands. That is a mark of an inferior hose clamp. The 316SS AWAB clamps are, IMHO, the best since they are made 316SS parts and used indented threading. See photo below. "
If the Titanium clamps are perforated, then I agree... I know Ti sheet metal very well..... I worked with it for many years. It is very crack prone compared with stainless. Unperforated might be good though.

Bash 19-03-2013 16:33

Re: When to replace thru hulls??
 
Quote:

Originally Posted by careka (Post 1189404)
Lubricate ?? with what, ?? oil, ?? or. Seacocks. ball valves,

I use white lithium grease for seacocks. You can get it in spray canisters, and apply during haul outs.

downunder 19-03-2013 16:36

Re: When to replace thru hulls??
 
1 Attachment(s)
Thru hulls and ball valves, not sea cocks on a Lagoon 400.

I would be looking at the link below at Compass Marine and consider installing flanged seacocks.

Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine at pbase.com


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