Cooling water intake blockage & quick cure.

Clyde_Wanderer

Clyde_Wanderer

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While motering into Rothsay this wk end, my cooling water intake got blocked but was noticed almost imediatly, but had to complete journey with aux o,b as it was too dark to sort problem, which I sorted next morning by connecting dingy foot pump to intake pipe and pumping until a huge burble was heard, and hey presto clear.
Infact this happened twice over the wk end, which got me thinking about some sort of quick, get me out of this situation cure, now what I came up with is, a twin skin fitting, perhaps 1-2 ft apart each with its own ball valve, both running through a Y branch to the single pipe, then to filter.
While motoring only one valve would be opened, so if it gets blocked you close it, then open the other and continue on your journey until such times as you can clear the blockage, as the chances of the two getting bloched within a reasonable time of each other is slim as you wont have any vacuam on the closed valve.
Any opinions?
 
Your idea will surely work, but does mean an extra hole in the hull, and every hole adds another risk: flooding from failure of skin fittings is not a rare occurence!
What about the normal grid over your intake? (bronze for preference) Do you have one? The commonly available cast ones have bars and slots of about the same width. They restrict the intake flow somewhat, and if that is already just adequate, engine overheat can occur. Widening out the slots with a power-tool and file can beat that problem without unduly weakening the grid.
 
a possible alternaive is to fit two valves and T piece downstream of your water strainer. The inline valve could be closed to stop water/air going to the engine and just upstream a T piece with a valve would allow the dinghy pump to be quickly conected. Not as convenient but just one skin fitting.
 
I agree with you about the second hole, but I found gratings over the intakes to be a pain after a while. They can get very clogged in some waters and I had barnacles growing on the inside at one stage. So when replacing my intake I got a new one with a grate, but drilled out a hole around the grate so that when/if clogged, I can unclog by wiggling a screwdriver from the inside of the hull - with this I get the best of both worlds
 
Had the same problem a few years back, luckily we were anchored at the time just getting ready to leave when we got the blockage. After many attempts to unblock the intake unsuccesfully I turned off the seacock removed the hose, joined it to a spare piece of pipe and then connected it to the seacock on the sink.
This repair although inconvenient with the hose across the cabin worked untill I could unblock the the main strainer
 
You could avoid drilling another hole in the hull by putting a T joint in the toilet water inlet hose. Or would this empty the toilet? Not if you have a siphon break air hole.
 
This is where an old-fashioned strainer in a standpipe came into its own. You could undo the cap, pull out the strainer, rod out the blockage, and replace , without even stopping the engine.
 
Another idea that I have adopted with Thames ferries that continually suffer blockages due to little shrimps (honest!) is to reverse the Y piece you propose and fit a valve above on both lines. Still have the normal sea cock but above it, one line goes to a large bucket strainer and thence onward to the engine. The other terminates in a pipe that fits your dinghy pump (or in the case of the ferries in question a compressed air line)
If the inlet gets blocked simply shut the valve going to the filter, open the other, give it a good blow through (if you will pardon the expression) and then reverse the valves for normal running. Saves another hole in the boat..... /forums/images/graemlins/wink.gif
 
We don't like grids, you can't poke down through them. I keep a long straight rod to push debris out, and a paint roller handle with the end bent into a hook to pull debris in. We don't clear with the engine running because there is a danger that weed will go in while the strainer is out. I still have to flush the oil coolers back through with the deckhose every now and then.
 
Clifford is right, the old-fashioned sort would be quite adequate for your 30-footer, and certainly works for me. I haven't upgraded to the plastic bubble version, just an unprotected hole then ball valve with a (previous owner's) mod leading to a vertical tube containing a cylindrical mesh. A quick turn of the wingnuts, slide top plate and seal round to one side, pull out strainer and remove weed/rag/poly bag, all in a matter of seconds.

So you happened to notice immediately did you? Should you ever worry about being too slow (off watch below with novice at the helm maybe) I recommend Halyard Marine's overheating sensors in exhaust and waterworks. Sensors plural?? Ah, you see, I didn't notice immediately . . .
 
Thanks everyone for all your input and advice.
But can cliffard explain the old fashond method better as I dont understand.
I can undo jublee clips on cock to filter hose and remove it blow it out and refit it in about three mins.
I would be very interested in fitting some sort of overheat early warning device. Anyone got ideas and or specs?
Thanks again.
 
Old fashioned seacocks have a standpipe on top. The water comes up the middle, goes through a tubular gauze into the outer skin of the pipe, and down to the engine feed. The top is held on with two wingnuts, you slacken them, swing the plate to one side, pull out the gauze and clear it. Some of the even older ones had a standpipe long enough for the top to be above the water line, so no need to close the valve for clearing. I have cleared one in as little as 30 seconds, in the middle of a race.
 
Thanks fisherman for that, I will look into it more in oct when she is lifted out, as I have never seen her out of the waterso dont know what set up is been used except that it is a boll valve type cock, and aprox 16mm ID hose to filter.
 
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