Hi All
Thanks for all of the comments regarding my problem of sometimes the boat pumps water and sometimes not. I'm amazed at the help provided. I think I have taken all into consideration in some form of test to try and debug this. I have disconnected the hoses carrying the water from various point where they enter the engine and tested to see if water is pumping and the water is getting through. Downstream of the pump I have put my finger on the hose and sprayed water around the cabin, ok, into a bucket, indicating good pressure from the pump. In all places water is coming, but since the problem is intermittent, what does that tell me? I feel confident that at least the problem is downstream of the pump. I've ordered a new thermostat, although the one that is in there seems to work fine when tested in water on the stove. Although it didn't seem to behave consistently after putting it back in. But I would think if it wasn't working water would still pump through the bypass but the engine would overheat. The engine starts immediately so I'm thinking compression should still be good, but mechanics are on order to check things like that. For sure it is blowing more black smoke on start up that it did a year ago, so something is amiss but could just be the injectors. I'll also get them to test the heat with a infrared thermometer. After doing all this, the last few times I've started the engine all has worked as it is supposed to. The problem is I've still not found a definitive cause. So has something fixed it, or not. And if not at what most inconvenient time will it manifest itself again, as on the west coast of Vancouver Island this summer? I thinking perhaps something is floating in the engine that sometimes plugs something like the thermostat, and sometimes not, depending on how it is floating around. The only challenge with that, is once the engine starts and is pumping water it continues to pump water, and I've run it for extended periods of time, travelling distances. So why wouldn't it plug it intermittently when running as opposed just when it is starting? So I'm thinking about the recommendation on using Barnacle Buster. It seems the easiest way is to take out the zincs in the engine as they recommend (and if anyone else has a 3GMD in a C&C 34 they know you can't really call this easy) and then put the intake hose into a big bucket containing Barnacle Buster and the outflow hose going into the mixing elbow back in the bucket and run the engine until the stuff has come through. Then let it sit for day. The alternative building a flushing system seems a fair bit more complicated but apparently is the more recommended method. Has anyone done this? Does it damage the impeller? What about all the stuff it dislodges? It seems getting that out of the system could cause more plugging up? I suspect this engine has never been flushed and it is a long ways from new. So will everything come out in small pieces or will there be big hose plugging flakes? Any help? Thanks Don From: dre...@gmail.com [mailto:dre...@gmail.com] Sent: May-24-13 7:41 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List Overheating 3GMD - the plot thickens Hi, My raw water cooled 2QM15 had a problem of intermitting over heating. I check and replaced many things: hoses, belts, impeller, ... I even pickled the engine with vinegar and turned over water pump impeller backing plate thinking the wear was limiting flow. I even thought I licked the problem. After a big trip (2 two-days gulf crossings), I left the boat for a few weeks and when I returned, the engine was seized. It turned out the head gasket was slightly blown which let raw water in the cylinder and over two weeks corroded/seized a piston. I discovered the real reason for the heating problem(and likely the reason for blowing a head gasket) when I fixed the engine: severe salt scale build up! The picture below is my block with the cylinder selves removed showing what was likely 33 yrs of scale build up. http://www.flickr.com/photos/dreuge/7782378010/in/set-72157631067396554 I happily rebuilt the engine(another story) but I strongly suggest that anyone with a raw water system regularly flush the engine with a good agent like barnacle buster (and don't cheap your self by using vinegar). The $30-$50 for barnacle buster is a lot less than the $800 I spent rebuilding my yanmar. - Paul E. 1979 C&C 29 Mk1 S/V Johanna Rose Carrabelle, FL Begin forwarded message: Date: Thu, 23 May 2013 18:00:17 -0700 From: "Don Jonsson" <dbjons...@shaw.ca> To: <cnc-list@cnc-list.com> Subject: Stus-List Overheating 3GMD - the plot thickens Message-ID: <023e01ce581a$0e7118d0$2b534a70$@ca> Content-Type: text/plain; charset="us-ascii" Hi I had previously sent out a message about an overheating diesel. The culprit, so I thought, was the knuckle going into the mixing elbow, because generally when I cleaned it, it worked again. For a while. So I finally took of the mixing elbow and gave everything a proper cleaning. I checked the water pump. I checked all hoses by blowing through them and the engine. I put it all back together and it all worked and water pumped like it is supposed to, except the water pump leaked a bit - needed a new gasket, but I knew that and just wanted to see if it would work. Got a new gasket and put it on. Started up and no water. I took out the thermostat and checked to see it worked - slightly corroded but it worked, i.e. opened in hot water. Put everything back together and started it up and a bit of water but too much steam. Took the thermostat out and put it in more carefully. Tried again, water running, no steam everything is perfect. Ran it for a while just to be sure. Turned it off. Waited a while (an hour) and started it up again. No water. So the problem is not the mixing elbow (and likely never was as it wasn't that bad). Not the pump as it looks fine. Not the thermostat - I don't think although I will replace it. The problem is sometimes the engine pumps water and sometimes not. And I'm stumped. This is a raw water cooled engine which makes things different. Has anyone had a similar problem and ideas for a solution. Also, it seems hard to get part numbers for a 3GMD and the local mechanic had to go find an old book. Is there any place online to find part numbers for that engine? Thanks to anyone that can help. Don
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