[Public-List] Engine cooling plumbing - Yanmar

[Jonathan Bresler]

Chris

Believe that the purpose of these loops and distances is to keep water from
backup up the exhaust system past the exhaust valves and into the engine.
The siphon break after the heat exchanger prevents water from being
syphoned into the heat exchanger via the engine cooling water inlet.
The distance from the mixing elbow down to the water lift muffler prevents
the water in the muffler from flowing into the engine when bow pitches down
(is this the correct?).
The rise in the exhaust after the muffler prevents a following sea from
flowing up the exhaust and into the muffler.  Were the exhaust outlet in
the stern to be hit by a several following seas, the repeated influx of
water could drive water into the engine.

Nigel Calder provides details on pages 474-477 of Boatowner's Mechanical
and Electrical Manual
https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330/

Jonathan

P.S. good to install a valve in the exhaust line after the muffler.
Constance had a frozen gate valve.  Replaced that with a 1-1/4" Groco ball
valve. On Constance, the exhaust line valve and the water intake valve are
always closed at dock.  Kinda feel I should keep them closed except when
motoring, but I leave them open while sailing....lazy I guess.  Also
concerned that I might start the engine, after sailing, with the valves
closed.

On Tue, Nov 28, 2017 at 8:31 AM, Andrew Johns via Public-List <
public-list at lists.alberg30.org> wrote:

> Chris,
>
> I would keep the vented loop in the raw water line between the heat
> exchanger and the mixing elbow.  The exhaust manifolds on these boats tend
> to sit very close to the waterline and you may not have 12in at all times
> (under sail).  It prevents water from filling the muffler and eventually
> engine with water when seacock is open and engine is off.
>
> Andrew
>
> On Mon, Nov 27, 2017 at 3:24 PM, Mike Lehman via Public-List <
> public-list at lists.alberg30.org> wrote:
>
> > The mixing elbow is a weak part of the Yanmar engine and needs replacing
> > periodically. As for the water line, you can estimate it to be about 3-4"
> > below the bottom of the sink.
> >
> > On Nov 27, 2017 2:33 PM, "Chris Martin via Public-List" <
> > public-list at lists.alberg30.org> wrote:
> >
> > >  Hello
> > > Please let me know when I reach my question limit. While I'm waiting on
> > > parts I started taking more the boat apart. I cleaned the heat
> exchanger,
> > > plan to replace cooling hoses and impeller and am thinking about the
> > mixing
> > > elbow. One thing I'm not sure about is the layout of the cooling line
> > from
> > > the heat exchanger to the mixing elbow. I've found a few opinions on
> > this,
> > > anyone gone through this lately? Yanmar 2gm20-f.
> > > I found this which is close to what I have
> > > http://i1121.photobucket.com/albums/l518/svsundowner/boatexh.jpg
> > >
> > > I need to figure out the waterline measurement, it doesnt seem like 12"
> > is
> > > an issue.
> > > I would like to remove this if only to simplify and reduce the number
> of
> > > connections/clamps. Just put it back the way it was, replace the
> > loop/vent?
> > > Or just straight shot from the heat exchanger to the exhaust?
> > > Also, my mixing elbow is soaking, anyone have a good source for these?
> > How
> > > long do they normally last? This is the first I've touched this part of
> > the
> > > boat so I have no idea how old it is.
> > > Thanks
> > > Chris
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-- 
Jonathan M Bresler
S/V Constance Alberg 30 #262
Annapolis/Eastport MD