seacocks - electrolysis nightmares, removing thru-hulls

[Cooper]

Hi. I'm new to this list. I have a 36ft custom mid 1960s sloop, strip plank mahogany with hand laid glass over. Beautifully made but neglected for a decade before I just had to save her - you know the story no doubt.
Electrolysis has always scared me, I have had a nasty feeling about my seacocks (best quality CW) even though the boat has a solid grounding bus system (the builder was an engineer), routine maintenance showed the rot has set in :(

The boat has far too many thru-hulls for my liking:
1. head in
2. head out
3. electric bilge pump
4. raw water in
5. sink
6. two cockpit drains
that's seven (!), plus the log and the two depth sounders, and the prop shaft of course.

So I plan to reduce that number asap, by -
- ganging 1, 3 and 4 with a single seacock, above which is a manifold with separate valves
- running cockpit drains out through transom - cockpit floor is above water level
- running sink out above waterline, or via the head out.

Does any of that sound crazy?

My big question - when I remove the now unnecessary seacocks, how should I fill the holes? I'm assuming a conical mahoghany plug, epoxied in with glass over, well filleted. Does that sound right? Or should I just replace the thru-hulls and cap them inside the boat?

Any advice gratefully received.
thanks
Simon

[Lew Barrett]

So I plan to reduce that number asap, by -
- ganging 1, 3 and 4 with a single seacock, above which is a manifold with separate valves
- running cockpit drains out through transom - cockpit floor is above water level
- running sink out above waterline, or via the head out.

Does any of that sound crazy?


Yes, a good deal of what you propose is poor practice, most particularly your first scheme.

If you do delete any through hulls, plug them and put a backing block within the hull. But it is generally considered poor form to share multiple functions with a single through hull.

[Breakaway]

Opinions vary, but I would not do what you propose. Heads are fussy as it is, turning simple plumbing into an octopus is a mistake. As for the sink and cockpit drain replumbing--will they drain when the boat is heeled? On both tacks?

Better to replace corroded fittings and get the boat squared away electrically. That'd be my plan.

[The Bigfella]

The number of holes isn't the issue. Its how they are maintained.

I'd venture that a well maintained seacock is more secure than a repaired hole more often than not too.

[Candyfloss]

1.&2. Don't mess with these.
3. You could shift this to above the waterline if it lets you sleep better.
4. You need this dedicated to your engine. With strum box, filter etc.
5. Best left alone.
6. Perfectly normal practice. Change to a thru-transom system only if your cockpit floor is well above above sealevel & already sloping aft. Which is unlikely.

In other words, what you've got is pretty much what everybody else has. Check your thru-hulls & stop-cocks carefully. Leave well enough alone.

[py]

I don't think I'd mix the head outlet with the sink drain. Call me fussy if you like. The rest sounds fine to me. My last boat, 52' steel, had just the one water inlet for engine, generator, 2 heads. Shower sink and basin all drained through one above water outlet. Both heads had seperate underwater outlets. Eng and genny above water exhuasts. She's still floating and she's now 30 years old. People worry too much. Particulalry about doing anything unconventional. Have you researched the bonding thing though? There seem to be 2 diametrically opposed schools of thought. Bond everything vs bond nothing.

[dhic001]

I'd be fitting new seacocks after cutting out all the bonding. Timber boats don't like being bonded, and a good amount of damage has been done by the practice. Fritha, when two years old suffered timber damage from being bonded for one year. This was after the original boatbuilder refused to bond her. The builder went through and cut the bonding, repaired the damage and she was ok for the rest of her time here.

Daniel

[wizbang 13]

Bonding makes no sense on a WB. One would need to bond all the hull fastenings .My bilge pumps go out on deck, my strip planker doesn't leak anyway. Consider Marelon over bronze, no brains /no headache ,no metal/no 'lectrolisis. This is over the edge for most,but my sink drains into a 5 gal. bucket. Great for saving water and for my wifes ti..uh....pecs .

[Candyfloss]

Sailed on a thirty footer to Tonga. Head & handbasin shared the same outlet. If you forgot to open the seacock, you'd pump s..t up into the basin. Niiiice.

[Hwyl]

There are lots of problems like that, for instance Cooper has head in, raw water in and bilge pump out on the same seacock. That would lead to flooding of the bilge, in which case worries about electrolysis would be irrelevant

[Cooper]

I'd like to thank everyone for weighing in on this thread. There does seem to be some variety of opinions. After consideration of all this sage advice, and sitting on the boat for a few more hours measuring and designing,

1. its clearly not advised to mix ins and outs.
2. obviously the raw water intake must be guarded, though I don't see why I could T- off the head raw in, with a stopcock inline.
3. I'd also consider putting in a Y valve in the line to the strainer to use the water pump as a bilge pump.
4. one side cockpit can drain via sink - yes there's plenty of depth, even at a heel, and I can put a second valve on the sink drain if there's any danger of feeding back up the sink and into the boat- which I doubt.
4. Elec bilge pump can feed out the transom- what's the point of pushing the bilgewater down and out the bottom of the hull anyway?
5. Head exhaust should stay solo - nasty story from Candyfloss - yuk!
6. that leaves my other cockpit drain, which I really want to get rid of, partly because they are so far back in the tight engine compartment that if something happened i couldn't get in there to jam a wood cone into them.

General: I can see that manifolds on seacocks is not 'standard practice', but frankly, I'd rather have one less hole in the bottom of my boat!

As py says, there's a difference of opinion about Now about grounding grounding/bonding. My boat was (once) very well grounded, with big fat copper to every metal thing. But I was advised by a surveyor and wooden boat owner to rip them off, pointing out existing evidence of de-lignification (ie destruction of wood integrity around thru-hull). I'm tempted to rip it all out, but presumably keep the anode on the prop shaft.

Since most boats spend most time on moorings/slips, why not hand a zinc over the side on a piece of wire - grounded to engine block or so?

And is the bonding tied to battery -ve?

Electrolysis remains a scary mystery to me. I found that the bronze center shaft of my bronze raw water strainer (below water level(!) has electrolysed badly - it was externally isolated form other metals but in contact with an ss mesh strainer. I though I had minimal potential for electrolysis - no aluminium to speak of, wooden mast, iron block, but a lot of bronze. I'm on a buoy, no neighbours, no shore power, so no stray current.

Tell me this, will a single metal item electrolyse in contact with sea water but not with another metal ? - I would have though not. If its Bronze, will the different metals in the bronze alloy electrolyse among themselves?

ok, thats enough miscellaneous brain picking for one post :)
thanks and best to all
Cooper

[pcford]

Forget about multiple sources for seacocks. If you want to put energy into your seacocks, see that they are properly maintained.

Bonding was popular twenty years ago or more. I believe it is fair to say that it has fallen out of favor and even is consider to cause more problems than it solves.

[Cooper]

"If you want to put energy into your seacocks, see that they are properly maintained." That's exactly what I intend to do when I get the current ones out, which are on their last legs. Which brings me to my next question, how to get them out. I saw a cute idea (captain pauley) - two hole saws on the one drill, the inner one centers the outer one to cut off flange on thru-hull. Any comments or suggestions?

[RFNK]

As py says, there's a difference of opinion about Now about grounding grounding/bonding. My boat was (once) very well grounded, with big fat copper to every metal thing. But I was advised by a surveyor and wooden boat owner to rip them off, pointing out existing evidence of de-lignification (ie destruction of wood integrity around thru-hull). I'm tempted to rip it all out, but presumably keep the anode on the prop shaft.


Bonding is definitely a bad idea. Delignification and problems with metal fittings are typical, I'm advised. You should keep the anode on the shaft but use a flexible coupling to isolate the shaft electrically from the rest of the engine. Don't link up any through-hull fittings electrically. Keep your through hulls but use only silicon bronze. Don't use stainless steel below the waterline. Get a copy of Nigel Calder's book on mechanical systems for yachts (find it on Amazon). Rick

[Candyfloss]

Don't use stainless steel below the waterline.

Except for prop shaft & rudder stock.

Oh, man, there is no consensus is there?

[Mark,SS]

Hi cooper , I,m going to bite on this one .
there is only only 2 inlets below the waterline
1, toilet inlet
2 raw water inlet for the engine
there is only one outlet below the waterline and that is the crapper !
The rest is BS !
Bonding ,forget it !
Skin Fittings ,Bronze .
Bronze is a noble metal and the pipe work is plastic so no electricity is conducted , so no earth is necessary .
Outlets , are another question .
Discharges should be above above the waterline .
End of Question !
Welcome to the game Mate on this one . This is the biggest ****e fights in motor cruisers .
I am of the Chris Mcmullan school of thought , ( the designer And builder of Fritha )
I will elucidate further if necessary , but don't be daunted , Have fun and please keep this going !
\Cheers Mark .

[RFNK]

Don't use stainless steel below the waterline.

Except for prop shaft & rudder stock.

Oh, man, there is no consensus is there?


Sorry, I meant for through-hulls. Also true for fastenings of course. Actually, I think the jury is back on bonding - a major no no! I should explain - stainless steel in saltwater is fine unless it's embedded, as is the case when it's run through timber as a through-hull or fastening. Crevice corrosion will occur in the embedded surfaces and the steel will break down. I've seen 316 SS bolts turned to powder even though they looked fine from the inside and outside. Rick

[Cooper]

I'm glad I joined this forum - my people! Thanks for all inputs and comments. I'm ripping the bonding out! MarkSS - yes, I'm with you, the less holes in my boat below wl the better I feel! I think I can significantly reduce the thru-hull count, by sending some things out existing transom outs, and ganging up a few inputs - without much trouble and without cutting new holes in the boat.
But, re "there is only one outlet below the waterline and that is the crapper !
The rest is BS !" - the only caveat is cockpit drains. I have the old stlye crossed hoses and deep set seacocks. But I have to say, the logic of the crossing evades me, even though I've done drawings of cockpit and hull cross sections at heel.
My cockit sole is above wl, but not by much. Not enough to permit drainage thru transom unfortunately, though possibly enough to drain through stern overhang, between wl and transom, if I were willing to cut a couple of holes in the hull. Not enough also, I think, to prevent water flowing in on a heel through a leeside thru-topside drain - I could, I suppose, fit a checkvalve (?)

I intend to replace with bronze. Someone was emphatic about marelon - no metal , no electrolysis - makes sense. I feel like a swift kick could break a marelon seacock off its thru-hull - I'm wary. Even if I used marelon seacock, I'd use a bronze thru-hull.

[Cooper]

So, moving on to the next stage - once I've got those nasty thru-hulls out of the hull (using the concentric hole saw method I think) how should I patch? Hull is handlaid glass over strip-planked mahoghany.

I'm planning - if I don't get any nasty surprises - to sand/grind the holes a bit conical (bigger on the outside) and epoxy-in pre-made mahoghany cones, flush with existing wood. Then sand/grind back existing glass for about 3" all round and glass and epoxy over. How's that sound?

Now for the thru-hulls that will remain -
I'm planning to use mushroom-shaped thru-hulls, but what if the thru-hull hole left by the old thru-hull is a bit big - due to delignification, say? Am I safe to fill a few millimeters (1/16/- 1/8") of slop with epoxy and chopped glass? If not, how should I deal with this?
thanks
C

[wizbang 13]

The marelon fitting I used(only have 1) has a substancial flange ,the thru hull and sea cock is 1 fitting. On cocpit drains, if they go out below the WL,fit venturis in front. I had a cocpit once,got knocked down and was standing knee deep in water that would not drain untill I stopped the boat. A coupl' o knots held the water from draining.