[C320-list] cooling water system

[Monte B.]

Very good raw water/exhaust side cooling check list Dave. I would agree that
all symptoms point to a raw water side restriction. The exhaust elbow has
been much discussed and led me to pull mine from a 3GM30 at 750 hrs. It was
heavily coked, somewhat restricted but not blocked. The sudden onset of the
problem would lead me to look for a foreign object in the system that would
restrict or block raw water flow which could be anywhere from the beginning
to the end. I believe I would start at the water inlet and confirm flow to
the pump and then downstream from there. Of course it will be the last place
you look but at least you will have an orderly troubleshooting flow and if
the fix is the last place you look you will have brought the entire system
up to snuff.

Monte
Laima #620

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of David Marecek
Sent: Monday, December 22, 2008 10:54 AM
To: C320-List at Catalina320.com; List Catalina
Subject: Re: [C320-list] cooling water system

Jim

I have just finished a complete overhaul of my cooling system on a 3YM30
Yanmar due to overheating . at 1400 hrs on the engine, My symptoms were
continuous weak exhaust water flow at all times and overheating at high
rpms.  End solution was a upgraded Heat Exchanger from Yanmar as they
had done a technical upgrade in 2004, and replacement of Exhaust Elbow
and Cleaning of Vented Loop.

Here are my findings since I have spent the last 4 months chasing
ghosts. Note most of these ideas came from people on this site as
suggestions, so I cant take credit for ideas, so I will list them in
terms of a priority failure analysis.  Note these are all related to
overheating due to visible  low water flow in the sea water cooling
system. There are many other items to check on the fresh water cooling
system, but based on your description of no visible water flow, I have
focused on sea water cooling.

1. Hose to Pump- This is usual suspect for sudden  loss of water.  A
Blockage of some sort-. Test all hoses by running water through them. 

2. Pump impeller-  this drives the water flow, so is top of list
especially if water flow slowed . There are appear to many ways this can
fail , blade cracks, spinning on the shaft,  etc which may or may not be
discernable. If the water suddenly stopped I would put this at top of
list and replace. However also can test by removing the output hose to a
bucket  and seeing if water is being pumped. This confirms pump is
actually getting power from engine.

3  If the impeller is pushing the water,  it can be pushed back by the
exhaust system.  
Vented loop. This tends to build up salt crystals towards the vent. It
also can be blocked with soot at the exhaust elbow end. Pull the exhaust
elbow end off the brass fitting  and inspect the inside . Also check the
brass fitting on the exhaust elbow as this will also collect soot. 
Take the valve in the port lazarette  off the hose and clean( Note this
is listed as a monthly maintenance item in the manual).
 If both ends are clean, disconnect at the valve and start engine to see
what comes out of hose at valve into a bucket. I got all kinds of junk
flowing into a bucket. Note in my case this was plugged with soot
solidly at engine end.

4 Exhaust Elbow- recommended replacement by Yanmar is 2 years, This
tends to soot up if you don't run at 90% rpm a lot.. When this soots up,
it restricts water flow  and also reduces engine performance.  (
Recommended running of engine is 90% of time at 90% and remainder full
power ) To check you can remove from engine (4 bots)  and check inside.
Note if the vented loop elbow is clogged with soot, high probability
exhaust elbow is clogged. I cleaned mine out as it was ugly at 1400 hrs,
however when I had service rep check, they recommended replacement as it
was getting thin in spots age 4 years.

5. Aqualift exhaust-  Drain to see how much water is in the unit. This
will tell you if water is getting this far. I didn't find any real good
tests for the unit. If it isn't leaking , it appears to function. Maybe
other readers have ideas on this one on how to test?

6 Heat Exchanger
This would be more symptomatic at high rpm as it would not be able to
transfer enough heat and you would find you would end up in over temp
alarm. .  If you get a sudden loss of water, this is low probability.
Symptoms here would be  over temp at high rpm  or slow cooling after
high rpm and normal running.  However if previous items have check okay,
any impeller pieces or other things can catch in the tubes as these are
small so it is worth removing and cleaning. However lowest on the list
for a sudden blockage.

7. Check exhaust lines from aqua lift to stern to ensure something
hasn't crushed them  in the stern locker.

8. Anti freeze mixture should be 50/50.  This helps ensure heat
exchanger is cooling at most efficient level. However this would be a
symptom of overheating at high RPM

9 Though not a symptom of low water flow, this can be a gremlin item.
Test the temp sensor and temp gauge and check wiring for ground faults.
If you are getting over temp  using a temp sensor with a gauge on it
from a service rep is a very good first check


-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of
james_delong
Sent: Saturday, December 20, 2008 1:02 PM
To: List Catalina
Subject: [C320-list] cooling water system

Next step please...

My Yanmar overheated the other day and we had to limp in to the dock.

Checked the intake seacock, cleaned the strainer, and hoses to the pump.
All ok. Pulled the pump and checked the impeller. Still in one piece.

I guess the heat exchanger is the next step. What is the process to
inspect it and what should I look for?

This problem appeared abruptly. Was OK the previous time out, but this
last time, limited water flow and when I started it today...nothing!

Thanks for all advise!!

Jim #453