Installing New Seacock's (A New Photo Based How To Article)

[Maine Sail]

Hi All,I finished another photo based "how to" article/blog based on the replacement of my through-hulls and sea cocks that I completed last spring.Take a look and let me know what changes I should make or if the instructions are clear enough for the average DIY boater.My intent with these articles is to help the average boater save $$$. The labor time involved in this job was a lot and would have translated into a yard bill in excess of 2k if I had paid my boat yard to tackle this job.I've had great responses, over 630 "thank you notes", just on my "Re-Packing A Traditional Stuffing Box" article alone so I continue to do them to help in any way I can.I hope this article helps as much as the others I've done..Here it is: http://www.pbase.com/mainecruising/replacing_thruhulls

 

[Steve]

New Seacock

Excellent. This takes threads of information I have read from a number of sources and puts it into perspective while addressing the how,why, and why not.I have to replace a seacock soon. I will be using this as my guide.Thanks.

 

[gfrazzle]

Seacock Tutorial

Great "how to"! My only comments would be:1)You might want to explain the procedure to countersink the backing plate for the flange.2)Including a link(s) to the source of the parts would be helpful.Fiberglass is obviously the best material to use for the backing plates. Would Starboard be an acceptable alternative?Thanks and keep the "how to's" coming. How about one on replacing a cutlass bearing?Links to your other tutorials would also be appreciated!

 

[Maine Sail]

To answer your queston

Starboard or it's many knock off iterations is NOT a good product to use as a backing plate.#1 It's far to flexible to offer any sort of rigid stiffening to the hull.#2 The manufacturer states that it does NOT stick well to anything including bedding compounds like 5200, 4200 or Sikaflex.#3 The concept of a backing plate is to become one with the hull, make it thicker and add stiffness so the seal between the hull and through hull is not compromised. Starboard fails in all these areas..Starboard is a great product for many uses just not one where bonding to another substrate is required or rigidity is required..

 

[Ross]

Mainesail, A very nice piece of work from the stand

point of the boat and with the photo essay. I added one comment conserning the need to clamp the work piece while cutting the blanks.Well done. Thanks.Ross

 

[Maine Sail]

Very good point Ross

Ross clamping the fiberglass board is a MUST and I did do that on my drill press but forgot to mention it. I'll update the site when I get home..

 

[Warren Milberg]

This is very well done article

Thanks for posting this item; it well done from both a content and visual standpoint. You take excellent images! You should think about sending to DIY Boats or a similar magazine for publication.I've found that the hardest part of this job is removing the old and cruddy thru-hulls. I've had mixed success doing this a number of ways. With someone on the inside holding a monkey wrench on the nut of the old mushroom, you can make a tool out of stock steel that will just fit the thru-hull opening. With a large wrench (or even a piece of pipe on the wrench handle) you can sometimes get the thru-hull to break free and turn and loosen. I've also had more luck using an angle grinder to cut a number of careful cuts in the outside lip of the mushroom then just bang the whole thing into the boat. This is a brute force approach used only when absolutely necessary. The key here is not damaging the hole through the hull so that you have to rebuild it when installing a new thru-hull.Finally, your first picture seems to portray an inline valve, rather than a true seacock (shown a few pictures below with flange) made of Marelon, mated to a bronze thru-hull. I know that Forespar and others state this is ok, but if it were my boat, I would not mix materials. While Marelon is a tough product, I don't use it for below-the-waterline applications since a friend of mine broke a handle off one while trying to shut a valve that was leaking....

 

[Maine Sail]

Warren....

Finally, your first picture seems to portray an inline valve, rather than a true seacock (shown a few pictures below with flange) made of Marelon, mated to a bronze thru-hull. I know that Forespar and others state this is ok, but if it were my boat, I would not mix materials. While Marelon is a tough product, I don't use it for below-the-waterline applications since a friend of mine broke a handle off one while trying to shut a valve that was leaking...."



If you read that first picture carefully I clearly state, for a number of reasons, why slapping a valve on a through-hull and not using a seacock is a bad idea including the mis-matched thread issues et.al. I also DON'T use Marelon because I too have broken handles off, four of them. It would be one thing if just the handle broke off but the handle holds in an o-ring and when the handle breaks the boat can occasionally start filling with water! While I like the theory and idea of corrosion resistant valves there are far to many reports of handles breaking off of Marelon valves for my comfort. I have stopped using them until I feel more comfortable. They DO offer great benefit but for me I am not comfortable with their answers to my queries about the re-design.

 

[Stillraining]

Great Job Mainsail

it seems that your procedure is time critical however. ( I'm thinking set time of the kitty hair here, unless i missed something.) You might mention availibal work time windows and the benifits of maybe having a second pair of hands for the first go. Just a thought as I was seeing myself atempting this.Again great job, I have one to do before spring and will concider your way of doing it now.

 

[David]

Thru hull

Good piece but new Marelon Have redesigned handle. I always recommend for below waterline.Also never mix dissimilar materials.

 

[Ross]

David, The concern with dissimular metals

is their place on the galvanic scale. The following is the galvanic series for stagnant (that is, low oxygen content) seawater. The order may change in different environments.Graphite Palladium Platinum Gold Silver Titanium Stainless steel (316 passive) Stainless Steel (304 passive) Silicon bronze Stainless Steel (316 active) Monel 400 Phosphor bronze Admiralty brass Cupronickel Molybdenum Red brass Brass plating Yellow brass Naval brass 464 Uranium 8% Mo Niobium 1% Zr Tungsten Stainless Steel (304 active) Tantalum Chromium plating Nickel (passive) Copper Nickel (active) Cast iron Steel Lead Tin Indium Aluminum Uranium (pure) Cadmium Beryllium Zinc plating (see galvanization) MagnesiumAny adjacent pair can be connected without harm. The farther apart they are on the scale the more likely you will get corrosion.http://en.wikipedia.org/wiki/Galvanic_series

 

[David]

Thru hulls II

Yes Ross but I mentioned dissimilar material not metals. ABYC does not recommend different materials on individual thru hull construction.

 

[Ross]

How does the ABYC feel about bronze thru-hulls in FRP hulls?

At some point a flexible hose will be connected to the assembly with a stainless steel clamp or two. We can't avoid mixing materials on a boat we can only try to be sure that they are compatable.

 

[Stillraining]

Ross;

This topic of Passive and Active metels can you enlighten me?Ps; I have tried to read about it but an not a metellurgist and can't understand what im reading.

 

[Ross]

Stillrainning, If you polish stainless steel or if

you weld it you destroy the chromium oxide coating on the surface and the surface is active and will corrode. When the oxide coat is restored the metal once again become resistant. This is one of the reasons that stainless steel develops crevice corrosion. If a corrosive solution remains in contact with the surface and there is no oxygen available to replenish the oxide film then corrosion can take place within the structure on the part. As you can see from the list it isn't a terribly large difference but in a critical situation it could be enough. A stainless steel bolt through a hole that stays wet is a good example of a situation that could allow this to happen. When it does failure is usually without warning. The visual appearance of the part will be fine.Copper alloys develop this oxide film rather quickly. For this reason when you want to solder copper you must clean the oxide film away before the solder will wet the surface. I hope this helps and I hope there is a metalurgist on here that will correct any miss statements I have made.

 

[Paul Brinkley]

galvanic series- use Ross's link to Wikipedia

and you'll get, among other things, this:"The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while electrically connected, the less noble (base) will experience galvanic corrosion. The rate of corrosion is determined by the electrolyte and the difference in nobility. The difference can be measured as a difference in voltage potential. Galvanic reaction is the principle which batteries are based on." You may substitute "passive" for "more noble" and "active" for "less noble", and this may be clearer. Active metals are more likely to corrode; passive metals are less likely. Two different metals which are electrically connected (or touching each other) in the presence of an electrolyte (water or some other conductive liquid) form a galvanic cell, and the more active metal (lower on the series listing in Ross's post) will corrode. Galvanic corrosion may be prevented in a number of ways, such as (1) sealing the surface with a non-conductor (paint, grease, tar), (2) removal of electrolyte (keep it completely dry- not really an option for boat parts), (3) plate the part with a more noble metal (gold, silver), (4) electrically insulate the two metals, or (5) use a sacrificial anode (a very active metal) which will corrode more readily than what you are trying to protect (this is why zinc, magnesium, or aluminum plates may be attached to metal hulls, propeller shafts, etc.) Special cases of galvanic corrosion can occur with a single type of metal in an electrolyte, if different areas have different concentrations of dissolved oxygen in the electrolyte. This is the corrosion that can occur on some area of a metal part that is not in contact with another metal. Aluminum alloys, if not protected by some means, are particularly bad for this.Hope this helps.

 

[CalebD]

Chiming in here I will say that this happened to me

aboard a friends Endeavor 32'. The black marelon valve handle went missing from my friends boat's raw water intake for the head. Fortunately we were in a slip so would have only sunk at the dock. I was able to turn it a bit but was rather perturbed when water was leaking in at some settings as I tried to close it. I left it in it's non leaking position of 'open' which was also potentially bad but it was in protected waters near Mayo, MD. The boat was owned by a consortium of 4 owners and I notified the most active owner of my concerns and he found the handle in the bilge about a week later. I do not think these valves are safe to use as thru hulls because of the possibility of the handle malfunctioning, in my limited experience.Ship happens.I've been reading way too much from Cap'n Ron's maritime lawyer's loss website: http://www.cargolaw.com/cargolaw.com in case that doesn't work

 

[Colin16557]

A related question

Okay...I have wondered about this long enough...When should you use a simple mushroom-headed through hull and when should you use one with a scoop/strainer? Also, should the slots/holes in the strainr face forward or aft?Or is this one of those "tastes-great/less-filling" personal preference things?

 

[Maine Sail]

Engine intake..

I don't feel a "scoop" strainer should ever be used on a sailboat engine or generator. If used however, according to Groco, they are to be installed with the slots facing backwards other wise they "catch" grass and can cause your engine to "Scoop" water and potentially flood it. If you MUST use an external strainer please use a non-directional ROUND strainer, not a scoop, preferably with a hinge.

I don't have one on my current boat. I have a 1" engine intake and have never had a problem with my intake plugging. I've had a "scoop" on another boat still fill up with grass, even facing aft, and it was very, very tough to get my line clear because I could not jamb a coat hanger or fish tape down there to clear the weeds because it would hit the "scoop"... If you do go with a scoop I'd advise the round hinged model so you can dive under, pull the pin, and clear the line if necessary..

Hope this helps..


A good basic rule of thumb for external strainers:

1) Never face a scoop strainer forward when installed on an engine or generator on a sailboat. You can FLOOD the engine and fill it with water if the seacock is open under sail.

2) While you are better to face a scoop backwards you can create added vacuum to the raw water intake and may shorten impeller life or compromise the cooling efficiency. I still find facing backwards better than a hydro-locked engine and have not come across a real situation that the added vacuum had any negative effect when impellers were replaced on a regular schedule.

3) ON sailboats use ROUND non-directional type strainers, preferably with a hinge, if you MUST use one. The round strainers will not force water into a non running engine and create no additional vacuum.

4) If you sail a catamaran or tri and have "scoops" and one engine goes down, or you normally run with only one aux to save fuel, you should ALWAYS close the non-running seacock or you will have a higher risk of flooding the non-operational engine.

 

[Ross]

I installed the scoop type thru hull with the openings

facing aft as recommended for sailing vessels in the instructions. The instructions further said to face it forward for fast power boats. The thing that needs to be watched for is stray bottom paint closing the slots in the strainer. I noticed that happening on Bietzpadlin before it became a problem and corrected it.