Capt. JG wrote:
"Frogwatch" wrote in message
...
My Yanmar 2GM was overheating because I could not get sufficient raw
seawater to flow through the heat exchanger. I cleaned the exchanger,
cleaned all lines leading to and from it, cleaned the raw water
strainer, cleaned growth from the water intake. I was able to blow
air thru from the top of the intake to verify it had no blockage. It
would start to pump and then soon be only a trickle. Replaced the
pump impeller twice too. WTF?
Finally, after months of screwing with it, I took off the raw water
seacock (problematic cuz she is in the water) and between the seacock
and hull fitting, found a piece of shell that would act as a one-way
valve when it got sucked into the seacock. I could blow downward thru
it no problem and it would initially flow upward too but it would then
lodge in the seacock blocking it.
SO, if you have raw water flow problems, you might check for this.


That's a interesting problem. How did it get past the screen (I'm assuming
you have one?) at the hull where the thru-hull comes, err, through? I've not
had it happen yet, but I could imagine a plastic bag getting trapped on that
screen. The only two ways to remove it would be to either stop the engine
and hope the plastic fell away or visit it personally.

I have a vertical type strainer directly on a ball valve seacock with no
external screen. Its 1/2" bore so a length of 10mm dowel might come in
handy. I'd get some water inflow, but nothing I couldn't cope with
holding a sponge in the other hand. I think the recommended solution
for plastic bags is blow back down it with a dinghy pump. Worst case, I
have enough hose on board to rig something from another intake.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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