Thanks for all the detail below vis a vis your anti-syphon setup.
When we get back to work on it Monday we may do some rerouting of the antisyphon loop, and relace the muffler with one having greater volume. But, having pondered the dates and circumstances of this last and the previous water lock, overnight I came up with a new theory. Over all the past years of sailing Itchen I ALWAYS closed the raw water intake when not running the engine, and especially so when leaving her unused for any length of time. Looking back, in both instances of wwater lock I had left the seacock open for quite a few hours, at least overnight. I think water is finding it’s way through the Johnson raw water pump ino the manifold and down into one or more cylinders.
Itchen’s Yanmar manifold is definitely slightly below the loaded water level.
Back to my previous practice from now on, shut the seacock whenever the engine is shut down, and make sure all crew are well-aware of the need to check and open the seacock before starting the engine! And, though I have never had this problem yet, consider shutting the seacock when bitter cold Maine weather leads to slow starting and extended engine cranking, to eliminate any possibility of pumping water into the manifold.
Prime suspect at the moment is either a
anti-syhon valve or not enough anti-syphon
height above waterline and manifold. And an
on-the- small-side water lift muffler. The
distances between waterline, engine, elbow,
anti-syphon valve are less than idea. but
Obviously more or less ok because this is a
occasional problem. Last time this happened
replaced the elbow and the anti syphon valve
declared the problem solved. Wrong.
I’ve in the past measured the head from the base
of the waterlift muffler to the top of the curve
of the exhaust hose (45 inches), but I’ve not
measured and noted the height of the vented loop.
Z’s vented loop is a Scot Pump, part number
890-913-VB-18F, from www.scotpumpflorida.com. I
last contacted them by email in 2014, when they
quoted me $18.80 for a new vented loop (funny,
when I now check my records I find I ordered a new
one in 2014 and Scot Pump never actioned my
I think that means I’m overdue to pull the vented
loop, clean it and re-install it and perhaps think
of buying about the only decent vented loop
available in Australia, a Nanni Diesel syphon
break that retails for about 5 times the Scot Pump
one (must be good, no?!)
Z’s Scot Pump vented loop is mounted as high as
possible in the engine room, on the forward face
of bulkhead #7.
Z was built with a Salisbury Hydro-Silencer SBM-20
waterlift muffler. WH Salisbury Co used to be
based in Skokie, Ill. But Honeywell bought the
company and refocused it to manufacture industrial
safety products. The Salisbury muffler has an
internal volume of 2.5 litre (2.6 quarts/0.66
gallon). If I need to replace I’d be looking at a
Nanni Diesel Waterlock muffler that has roughly
double the internal capacity.
maintenance, especially a VHF antenna SWR
Easily and expensivly fixed, I expect.
For our first Zygote, I had a SWR meter and I used
to check such things. With Z, I’ve not once had
reason to think about it!
Last year when we pulled the mast, repainted it,
replaced a length of conduit inside, etc, I
replaced Z’s original masthead VHF antenna (and
ran new cable, replacing 15 year old RG-8U with
But again I didn’t measure SWR. What symptoms have
- SWR error messages every few minutes from the Vesper Watchmate 850 AIS transponder, echoed by the Raymarine C80, driving us crazy with insistent alarm beeps.
- Miserable output from the ICOM IC-M506. Had a very experienced electronics guy go over it all yesterday with professional meter and dummy load, and found:
a) a short in the radio to mast heel run of cable, hidden during a recent water tank replacement installed when I was not around to advise on where to rerun the old cable.
b) only 11+ volts power at the radio - which was putting out 17 watts instead of its rated 25W – so I willcheck connections and maybe up the size of the feed line.
c) Marginal, not terrible but not great SWR and output readings for the mast cable and masthead antenna, even though the connections looked good.
So will sort out and fix all that come Monday.
BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland,