On Mon, 19 Jan 2004 16:28:18 -0500, "Jeff Morris"
wrote:

I've never opened the heat exchanger on my Yanmar - I've done it on a Westerbeke
without too much hassle. You should be able to remove the end caps while its on
the engine. However, pull the hose that feeds the elbow and repeat the flow
test. This will tell you where the problem is. Its a bit of a pain because
the elbow fitting has a little ridge on it - this might be a good time to add a
"hose pick" to the tool box. Its like a screwdriver with a bent point for a
tip - you work it around to loosen the hose.

On other thing to invest in is a parts book. This includes blowup diagrams of
everything so you can see what you're up against. Torrenson is a good source,
as is Mack Boring or Mastry in the USA.

Good advice. Also, the Yanmar Service Guide is excellent, and not too
expensive. For instance, it tells you exactly what volume of water
you should be pumping.

For the original poster, opening the heat exchanger is usually pretty
easy, but I think it's your last resort. Since you say you are
getting no waterflow at all, the heat exchanger core is not my first
guess for the problem. It has a lot of small tubes, any one of which
is easy to clog, but the rest would still be open. The core is over
$1000 to replace, so I wouldn't screw with it unless I TOTALLY knew
what I was doing.

If you do have to do it, you'll probably need to remove both end caps.
Look carefully at the caps and the gaskets and the packing. You'll be
glad when it comes time to put everything back together. If you're
lucky, the core will slide right out. If not, you'll need to force it
with something like a large wooden dowel. It's a tight fit by design.
If some deposits have built up around the core, it can be a real pain.
Be careful. $1000! Theoretically, the core can slide out either
direction, but the engine box will probably leave you only one way to
go. You'll probably need to remove the exhaust pipe as well as the
end caps, so this might be a good time to replace the mixing elbow we
talked about.

The question now is what are you going to do with the core. You can
rod it out, carefully. The copper tubes are not really strong. If
you need to clean it, you can take it to a radiator shop as long as
they don't use acid. A good acid bath will leave you with an
interesting metal tube to play with after you install the new core you
bought for over $1000. (Have I mentioned that it's over $1000?) You
might try Marsolve, but I have no experience with it.

Finally, internet advice is worth what you paid for it. If you bugger
it up, it's not my fault!

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