Peter, this is one of those tasks which has to be approached with a plan. I have been through it a few times and finally found a little piece of a real old, brittle, and rusty impeller in the little hose which goes from the water pump into the engine...... lots of frustration. In over 20 years of ownership, I had never had an impeller come apart, so it had to be something prior to my ownership. It would sound the whistle at random times, and I could never find a cause until I started from the input and followed it through.
Start at the water inlet. Shut off the seacock and pull the hose. Then open the seacock and let some water in. It should squirt pretty strongly, as the through hull is rather small, at least it is on my 30-1. If that appears OK, then put it back together and pull the hose off the input side of the filter. Check again. Continue in small increments (each hose from start to end). I always thought that I had adequate water flow until I found that little bugger and when it was pulled out, I realized that I was always at about 75%. My engine is a 2QM15. Gary ----- Original Message ----- From: S Thomas via CnC-List To: cnc-list@cnc-list.com Cc: S Thomas Sent: Tuesday, September 08, 2015 2:43 PM Subject: Re: Stus-List Diesel water alarm question It is pretty hard to judge the flow rate coming out of the exhaust by eye, and I have been falsely lulled into thinking that all was well in that department on more than one occasion. It absolutely could be a problem with your thermostat or temperature sensor as others have suggested, but it is far more likely to be a problem with the rate of raw water flow in my experience. In addition to cleaning out the strainer you should check for a partial blockage at the intake or between the intake and the strainer screen. A small piece of twig can get in there and slow things down without stopping the flow completely. It is fairly easy to disconnect the hose from the filter and flush back out through the through hull using a dock hose. The one place that this does not get is passage in the strainer housing itself, and sure enough I had a piece of wood get stuck in there one time. Took quite a while to find it, and in the meantime I bought a new thermostat and a new temperature sender. About the only common way to get debris downstream from the raw water strainer is if part of the pump impeller breaks off. It should be checked if cleaning out the strainer and the raw water system that leads to it does not fix the problem. Steve Thomas C&C27 MKIII Port Stanley, ON
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