More Seacock Questions (srry)

Feb 6, 2011
253
Well with all weeks and weeks of snow, I finally was able to get over to the boat and finish removing the old gate valves and thru-hulls. I had to resort to just about every possible method mentioned on this discussion to get them all out. But I now have 5 new holes in the bottom of my boat. Time to get serious about filling them back up.

I need advice on how to proceed. I'm pretty sure that I will be installing a fixed head, "Someday", so I will be installing seacocks on the two holes for the head. I will be using Forespar Marelon seacocks and thru-hulls. I will have to enlarge the intake hole to 3/4". I will be using Forespar Marelon thru-hull and seacock for the sink output. My uncertainty is what to do with the sink input and the engine cooling input.

My choices are:
1) Install a seacock over both holes, keeping engine and sink separate.
2) Install a seacock in engine compartment, for both engine and sink, and plug up sink hole.
3) Install a seacock over sink hole to use for both engine and sink, and plug up engine compartment hole.

My original plan was to do #1, since this involved the least amount of modification to the boats systems. But then I found out that seacocks, small enough to fit the original holes, don't exist. Forespar does offer a 1/2" product that claims to be a seacock, but there is not mounting flange, it just screws on the thru-hull. However, I would like to have all seacocks through bolted. So I was looking at installing two 3/4" seacocks which seemed like overkill. One 3/4" seacock for both the engine and sink seems more reasonable.

Someone here mentioned that they had done option #2. So I started to think along these lines. I did a fit check of the 3/4" Forespar seacock and it seems like it will work, but it will be kinda cramped. Especially when you consider the plumbing that will be added on top to provide water to the sink and to provide a fill tube for winterization. Because the surface curves away from the seacock (instead of curving inwards like all the books show), the shaping of the backing block might be tricky. It will need to be rather thick on the ends to provide at least a 1/2" of block right under the seacock. While contemplating the fitting, I started to have doubts about having that plastic seacock right there in the engine compartment. I started think about "What if" scenarios. I started to think about what might happen if an engine fire occurs, etc, etc. So if I put it there, I might want to go with bronze. I haven't seen an Conbraco Apollo seacock in person, but I just looked up the data sheet on their website. Although the body looks like it might be a bit smaller, the flange appears to be the same size as the Forespar, the handle appears to be about the same distance from the center, and the height seems about the same. So it seems that their seacock would take up about the same amount of space.

While contemplating all this, I asked myself the question: Why don't I just use the sink hole instead?? Thus option #3.
Benefits:
1) Seacock is not near engine, that could possibly be on fire.
2) Access to Seacock is easier.
3) Lots of available space for plumbing.
4) I would feel better using the marelon seacock instead of bronze.
But:
1) I would need about 2-3 additional feet of hose between the seacock and the engine. How would this affect amount of water drawn? It seems to me that any effect, on my current MD6B, would be offset by having a larger hole/hose for water. Opinions Please!! (For those Beta installs, does Beta have a recommended maximum hose length for engine cooling?)
2) Either option 1 or 2 would require cutting a hole through the padding and the bulkhead between the engine compartment and the sink cabinet. I am assuming that padding is not only sound insulation, but fire proofing as well. So I have some concerns about that as well. However, I think that if I make the hole just big enough for the hose, and either a tight fitting grommet or some sort of sealant, that it should be ok. What do you think?

Sorry for writing a book to ask two questions. Guess I'll post this now. Thanks.

Chris
V-2933[Non-text portions of this message have been removed]
 
Apr 30, 2000
197
For what it's worth, I used a single seacock to supply water to the engine,
and (rarely used) to the seawater pump at the sink. A check valve was
installed to keep from sucking water and air back from the sink pump when the
engine is running. The hose runs from the seacock to a strainer and then to
the engine and sink pump. My Vega is older and had a hole on the port side
bilge that I used for both. I plugged the hole in the engine compartment
with a bronze carriage bolt and 3m 5200. Works great. I'm happy with
Conbraco seacocks. BBach V1071
 
Feb 6, 2011
253
Thanks for the info, Bill. What would you estimate was the extra length of hose needed to move from the engine compartment hole to the one in the bilge? My Vega has the sink input hole under the starboard seat, just forward of the sink cabinet.

Chris
 
Apr 30, 2000
197
I think maybe 3 feet. The length is not important as long as the hose is big
enough. The critical thing is not to create any head difference that the
pump has to work against. As long as you make the hose from seacock to
strainer about 3/4 inch, you'll have all the water to the pump that you need.
Put the strainer (Groco 500 is plenty) just above the waterline so you can
clean it without water loss. I put mine in the engine compartment high on
the port side. It just fit with my Yanmar 2GMF. I don't know about Volvos.
I'll try to post some pictures in the files section next weekend. Bill
Bach V1071
 
Oct 31, 2019
70
Hi from an engineering point of view--keep engine water separate both supply and discharge. I work in large utility services and believe me, cross-over or redirected flows will cause you large and $$$ headaches. I really enjoy this sharing of info--I have my 26x mcgregor forsale and hope to go to a fixed keel boat. jorgen
 
Jul 24, 2002
149
As a newbie, I am really in no position to give advice on seacocks etc.
However, I have heard (and it makes sense to me from a Physics point of
view) that the danger with sharing the raw water intake with anything
else is that if you forget to close the valve to that "anything else"
(sink etc.), you risk sucking air into the raw water flow to the engine
(this is actually a pumping method!). The problem is that you might not
be able to tell that something isn't right - water comes out the back
without apparent obstruction, yet (at least hypothetically) you could
end up with too much air to get sufficient cooling...
Am I wrong on this? - Sebastian
 
Nov 8, 2001
1,818
Hi All

I now have a new stock of the Transom Venst. There is a photo on the Yahoo
Photo page for all those who have not seen them. They are exact copies of
the originals but are better UV protected. Email me for prices etc.

steve@...

Kind Regards

Steve Birch Vega "Soutehrn Comfort" V1703
 

mocap1

.
Oct 31, 2019
96
You are correct; however, if the T were below the waterline, close to the
seacock so that it was always flooded, I think it would be safe enough.
Personally, I think it would be poor practice, and would rather have the
additional hole in the hull.

Mort
 
Oct 30, 2019
61
Hi-

This brings up a good question. I am also renovating my Albin, and was
thinking about combining the thru-hulls for the sink and engine intake. My
question is this- The original engine intake thru-hull passes through the
leading edge of the engine bearers. I've used proper seacocks with backing
plates on all of the rest, not the bastardized ball valves on the end of
thru-hulls.

How are others attaching these thru-hulls? Pick a different spot?

Dave- Albin #2917
 
Apr 30, 2000
197
Hello- As I related in an earlier post, I combined engine water and sink
input in the same seacock, relocated to the bilge. I put a check valve in
the sink line to prevent backflow of air (there's already a one-way flap in
the foot pump, so this is redundant to some extent) and made the line plenty
big to keep suction pressure to a minimum. I think the bilge location is far
superior to the original - puts the intake lower and allows much more room
for the backing block. Just my opinion.