water leak from raw water cooler

[dash]

260 express, 6lp yanmar..raw water is leaking from the endcap of what I guess is a heat exchanger. There is a nut or bolt at the center of the endcap. I discovered the leak while underway and felt around trying to find the source, the water was not hot even though the engine was at normal operating temperature. I headed straight back but never noticed any overheating. Looking forward from the top the aparatus is on the right side of the engine. It also has a zinc in it which I replaced just 25 hours back. Any ideas of what is happening and why?

[Pequod]

Did it leak before you replaced the zinc? The bolt merely holds the end cap onto the end of the bundle(13mm. bolt).

[dash]

Not that I know of. The zinc is not leaking, it is located on the other end of the unit over on the side where one can see it pretty easy. The leak is coming from underneath right at the front end of the unit and there is a short hose right in the way and just above where you can't see.

[dash]

I used a flashlight and mirror trying to see where the water is coming from and it appears that it has been leaking under the heat exchanger for a while. I see lots of surface rust on the engine and surrounding parts. As this boat came from the northeast coast, I suspect that it froze at some point and must have a crack. To look at it from the top side one would never know it was leaking. I've been getting bildge water ever since I got the boat but thought it was a normal amount.
I will just remove the heat exchanger and maybe that will reveal the problem. Any tips on removal would be appreciated.

[Kurt]

dash...

I'm not familiar with Yanmar Diesels but...

Is it possible that the endcap gasket is leaking? If you remove the center bolt, the cap should come off and you can take a look in there. It may be a multi-pass H/E so make sure you note the orientation of the gasket. After removing the cap, you will almost certainly need to replace the gasket even if it's not visibly damaged since it'll probably be somewhat crushed and deformed.

Taking a gander at this may save you the work of pulling the whole heat exchanger out.

[dash]

that's a good idea. I'll try that first.
thanks for the advise.

[Pequod]

Please buy a new end cap gasket before you remove the endcap. The gasket is not re-usable. Also examine the heat exchanger tubes in the bundle to ensure there is no blockage. Removing the heat exchanger involves dismantling half the port side of the engine as well as the starter.

[dash]

Thanks for the advise. It turned out to be the end cap. It has been over tightened causing a stress crack from one side to the other. I'm wondering if there should have been an interal washer to keep one from tightening to the point of cracking the end cap? Anyhow, it's fixed now..
thanks

[Kurt]

That's better than some of the other possibilities! Glad it's solved.

[mymojo]

Dash,
I have followed your thread with some trepidation as I think your boat was my boat - the former 'another Irish Wake' and I was hoping that you did not have any issues that were too severe. I think the boat was winterized since new by the original dealer that sold it new so I had hoped they did not cause anything to cause a freeze up and cracking. I dont think the exchanger had ever been serviced at least thats what I remember from my discussions with the selling dealer-I wonder if the issue of over tightening has existing from day 1?
I'm happy things have worked out for you and hope you're enjoying the boat-I can tell you I miss the simplicity of a single diesel.
Best,
Greg

[dash]

Hi Greg, The boat is preforming very well with economy as the number one asset. We go fishing every Thursday, as long as wave height is less than 4', we have several good spots that we like to fish anywhere from 5 to 25 miles out. I keep the boat on a lift and wash down after every use. We now have 264 hours on the quatz hour meter and expect to have many more hours of use before any major issues. I just changed oil and filters and cleaned the raw water glass filter and replaced all the zincs that I can find. Sorry about running on but I thought you might like to know that your old boat is being taken care of and is taking care of the new owner.
another Irish Wake, out..

Oh btw, if anyone knows...what should I do about the surface rust on and around the engine due to this leak that I'm repairing?

[mymojo]

Glad to hear Dash - many more hours than I managed to put on her!
For the rust I have used a dremel tool with a wire brush followed by a de-glosser liquid on a rag and the spray paint made for my volvo motors. Perfect match to the original volvo green - I'm sure they make the same stuff for Yanmar engines.
Have fun --- wait sounds like you are!

[26Stalker]

I had the same issue 30 miles out and it turned out to be the end gasket. Run 5 miles, shut down, let the bilge catch up, run 5 miles let the bilge catch up, shut down, but I got home. The Yanmar guys were pretty embarassed at the gasket supplied by the factory.