Just posted on other thread YES a real PITA to get to and replace on my 3HM as
well $678 bucks later its done ! ouch!! ☹
John Conklin
From: CnC-List on behalf of Nauset Beach via
CnC-List
Sent: Monday, May 28, 2018 10:53:45 AM
To: cnc-list@cnc-list.com
Cc: Nauset Beach
Subject: Re: Stus-List thermostat on 3QM30H > Exhaust Elbow Cleaning
Rick &/or anyone else,
Is there a recommended “service interval” for checking / cleaning the exhaust
elbow on a fresh water cooled 3GM30F? Mine was last checked 3-4 years ago and
have probably had 100+ hours operation during that period. It is a real PITA
to access / remove / reinstall that elbow.
Thanks,
Brian
From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Rick Brass
via CnC-List
Sent: Monday, May 28, 2018 10:16 AM
To: cnc-list@cnc-list.com
Cc: Rick Brass
Subject: Re: Stus-List thermostat on 3QM30H
Bill;
A “raw” water cooled engine passes water from outside the boat ( in your case
lake water) through the engine for cooling. A “fresh” water cooled engine has
antifreeze in the engine and a heat exchanger, and the lake water only passes
through the heat exchanger to cool the antifreeze circulating inside the engine.
Josh’s note about making sure you have the correct thermostats installed in
your engine is spot on.
A raw water engine uses a low temperature thermostat and has a low operating
temperature. I would have guesses 120-125, but Josh found a spec of 108 for the
thermostat. Your operating temperature when the engine is under load should be
around 140-145. That helps to prevent deposits inside the engine that will
block the cooling passages.
A fresh water engine runs at a higher temperature – diesels are more efficient
at higher temperatures. You use a 165 degree thermostat and the engine can get
to 180-190 under load.
One consequence of the lower temperature in a raw water engine is that there is
increased production of unburned hydrocarbons and soot. Back in the day, when I
was a Yanmar certified technician and teaching diesel mechanics, the consensus
among the mechanics was that the exhaust elbow on the Yanmar 2 and 3 cylinder
marine engines should have the carbon buildup cleaned out every 50 to 100 hours
– at least yearly – as preventative maintenance.
On a raw water engine like yours, that would be a very good idea.
Rick Brass
Washington, NC
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