A while back I had a guy put a temperature gauge on my Yanmar. I thought
he installed it incorrectly until last weekend. A guy loaned me this
slick hand held temperature laser gauge thing which he said to aim at
the thermostat body for the running temperature of the motor. It read
115. The installed gauge starts at 120. Once I shut off the motor I
switched the key back on and it read about 135 on the installed gauge.
Must have warmed up once the water wasn't running through it. So the
installed gauge works, but the motor pretty much never gets up to 120.
And I mean never, when it's running, even when I have it full throttle,
pushing the boat along for hours!

So my question is this: A nearby very experienced boat refurbisher guy
with alot of Yanmar experience said I should decrease the flow in the
raw water sea cock until the temp reads 140-160. He said some diesel
motors use this method (Perkins I think he said). He said I shouldn't
mess with the thermostat because it was easier to just decrease the
water flow through the sea cock. This won't hurt the water pump? I
asked. No, he said.

So, good idea? Is it a big deal to keep the motor running warmer? Bad
idea to decrease the flow through the ball valve sea cock? What do you
all think?

Stephen

On 2008-08-01 02:35:06 -0400, Stephen Trapani said:

A while back I had a guy put a temperature gauge on my Yanmar. I
thought he installed it incorrectly until last weekend. A guy loaned me
this slick hand held temperature laser gauge thing which he said to aim
at the thermostat body for the running temperature of the motor. It
read 115. The installed gauge starts at 120. Once I shut off the motor
I switched the key back on and it read about 135 on the installed
gauge. Must have warmed up once the water wasn't running through it. So
the installed gauge works, but the motor pretty much never gets up to
120. And I mean never, when it's running, even when I have it full
throttle, pushing the boat along for hours!

So my question is this: A nearby very experienced boat refurbisher guy
with alot of Yanmar experience said I should decrease the flow in the
raw water sea cock until the temp reads 140-160. He said some diesel
motors use this method (Perkins I think he said). He said I shouldn't
mess with the thermostat because it was easier to just decrease the
water flow through the sea cock. This won't hurt the water pump? I
asked. No, he said.

So, good idea? Is it a big deal to keep the motor running warmer? Bad
idea to decrease the flow through the ball valve sea cock? What do you
all think?

Stephen

By its output (15 hp), I believe yours is a raw water cooled engine.
Water temps must be lower or you'll suffer deposits that'll make life
less than primo over time.

Yanmar had a great rep before they switched to closed-loop fresh water
cooled engines that like higher temps. My experience of the later
version tells me that they know what they are doing -- no problems not
fuel related in 1500 or so hours. I'm not exactly OCD on that subject
as it's never failed us in 16 seasons of fairly heavy usage.

If people with direct experience respond, of course listen to them.

--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

Everything I have heard, and my experience with my 1979 2QM20, is that the
QM Yanmars are among the coolest running diesels ever built. It's kind of a
mystery how they manage to diesel at all. Still, my engine runs perfectly
30 years after it was built. If I had just spent thousands to repower, I
would be estatic with it's performance.

I took my old thermostat out after three seasons and it failed the heating
water in a pan test. The engine had been running fine though. Engine
vibration not present in the pan on the stove may have been helping it
along. I put in a new thermostat and have detected absolutely no change in
engine performance or exhaust color.

Smile, sail, be happy, don't worry. Point the laser temp gauge at your wife
or girlfriend instead and make some wisecracks to see where they lead.

--
Roger Long

On Thu, 31 Jul 2008 23:35:06 -0700, Stephen Trapani
wrote:

A while back I had a guy put a temperature gauge on my Yanmar. I thought
he installed it incorrectly until last weekend. A guy loaned me this
slick hand held temperature laser gauge thing which he said to aim at
the thermostat body for the running temperature of the motor. It read
115. The installed gauge starts at 120. Once I shut off the motor I
switched the key back on and it read about 135 on the installed gauge.
Must have warmed up once the water wasn't running through it. So the
installed gauge works, but the motor pretty much never gets up to 120.
And I mean never, when it's running, even when I have it full throttle,
pushing the boat along for hours!

So my question is this: A nearby very experienced boat refurbisher guy
with alot of Yanmar experience said I should decrease the flow in the
raw water sea cock until the temp reads 140-160. He said some diesel
motors use this method (Perkins I think he said). He said I shouldn't
mess with the thermostat because it was easier to just decrease the
water flow through the sea cock. This won't hurt the water pump? I
asked. No, he said.

So, good idea? Is it a big deal to keep the motor running warmer? Bad
idea to decrease the flow through the ball valve sea cock? What do you
all think?

Stephen

Your 2QM15 should have a thermostat, part number 124770-49200 (Raw
water cooled engine) and a 46150-004531 over temp sender. Operating
temperature should be in somewhere around the 140 - 160 deg. F. range
but the idea of closing the water inlet to control temperature is not
something that is usually done. Certainly I've owned and worked on
Perkins engines for years and this scheme was never recommended by the
factory or any installer I ever came in contact with.

Just go out and buy a thermostat and install it, it is right there on
the front of the engine and easy to get to.

I'm not 100% sure, but I believe that the over temp warning sender on
a raw water cooled engine is set to 180 deg. F. But you should check
this figure as it has been some time since I worked on a 2 cyl.
Yanmar.


Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)

Stephen Trapani wrote in news:x8ykk.4570
:

So, good idea?

The motor runs great....

It hasn't had a problem in a long, long time.....

There's nothing we can find wrong with it.....

Why is it boaters have just GOT to screw around with something on the boat
that works great.....creating, of course, a disaster down the road?

Now, be a good boy and change the oil. After you change it, put a lock on
the engine compartment hatch and give the wife/girlfriend/mate the key so
YOU can't open it until it's time to check the oil again. We've instructed
her to ignore your whining and begging for the key, telling her if you are
allowed near the engine you're gonna screw it up and strand her on some
sandbar.

....There.....much better.

IT'S FINE....GET AWAY FROM IT!

http://www.youtube.com/watch?v=TNXlyE05Eh8
http://www.youtube.com/watch?v=9wcMdqGVuS4
http://www.youtube.com/watch?v=la9hr3D0RDI
http://www.youtube.com/watch?v=0iwrroFq7UI
http://www.youtube.com/watch?v=3jxaX74yHlg

Look how nice they run without someone screwing around trying to mess them
up!

"Stephen Trapani" wrote in message
...
A while back I had a guy put a temperature gauge on my Yanmar. I thought he
installed it incorrectly until last weekend. A guy loaned me this slick
hand held temperature laser gauge thing which he said to aim at the
thermostat body for the running temperature of the motor. It read 115. The
installed gauge starts at 120. Once I shut off the motor I switched the key
back on and it read about 135 on the installed gauge. Must have warmed up
once the water wasn't running through it. So the installed gauge works, but
the motor pretty much never gets up to 120. And I mean never, when it's
running, even when I have it full throttle, pushing the boat along for
hours!

So my question is this: A nearby very experienced boat refurbisher guy
with alot of Yanmar experience said I should decrease the flow in the raw
water sea cock until the temp reads 140-160. He said some diesel motors
use this method (Perkins I think he said). He said I shouldn't mess with
the thermostat because it was easier to just decrease the water flow
through the sea cock. This won't hurt the water pump? I asked. No, he
said.

So, good idea? Is it a big deal to keep the motor running warmer? Bad idea
to decrease the flow through the ball valve sea cock? What do you all
think?

Stephen

If your engine is fresh water cooled then the best operating temperature is
about 180 degrees. You can even go higher if the FW system is pressurised
with the sort of pressure cap you find on cars.
However, if it is salt water colled anything over 130/140 degrees is too hot
as it will bring deposits out of the salt water that will block the cooling
passages.
I do not think it is a good idea to regulate temperature by throttling back
the salt water system by partially closing the inlet valve as the pump is
most probably a rubber vane type positive displacement pump and this will
shorten the impeller life.
If FW cooled there should be a thermostat on the FW side that takes care of
the temperature.
If SW cooled the way to go is to fit a bypass around the pump with a valve
it so that excess water can be passed back to the suction side of the pump
and does not go through the engine.. Adjust the valve to bypass the right
amount of water to give the correct temperature in the engine.
To work this system properly you need a temperature gauge on the engine
since it is important not to go above about 140 degrees.

Thank you all for your opinions about my raw water cooled Yanmar.

If I just let it do what it's been doing for thirty years, eg, running
below 120, Is it bad to let it run at idle for long periods? I would
like to use it as a generator sometimes while I'm using my 1500w
inverter or just to charge the batteries. I had previously been under
the impression that it was a bad idea to run it for very long without
engaging the prop because the motor runs so cool, so I tried not to do
that much.

After observing the temperature gauges (installed and manual) it seems
that running it engaged doesn't really warm it up much! Crazy.

So, bad to run it at idle much?

Stephen

On Fri, 01 Aug 2008 18:03:18 -0700, Stephen Trapani
wrote:

Thank you all for your opinions about my raw water cooled Yanmar.

If I just let it do what it's been doing for thirty years, eg, running
below 120, Is it bad to let it run at idle for long periods? I would
like to use it as a generator sometimes while I'm using my 1500w
inverter or just to charge the batteries. I had previously been under
the impression that it was a bad idea to run it for very long without
engaging the prop because the motor runs so cool, so I tried not to do
that much.

After observing the temperature gauges (installed and manual) it seems
that running it engaged doesn't really warm it up much! Crazy.

So, bad to run it at idle much?

Stephen

You are going to get a thousand reply saying "Horrors! Don't ever let
your engine run at idle!!!!!! It's terrible; Terrible!"

If you want to be scientific it is likely that running a diesel engine
for long periods at very low RPM, and probable resulting low block
temperatures, is undoubtedly not the ideal practice but in real life I
notice that welding machines, trucks, heavy equipment, dry land
generator sets, drilling rigs, and just about every other diesel
engine in creation are run at idle for long periods with no noticeable
problems.

Probably, if you are running your propulsion engine to charge
batteries you aren't running it at idle anyway. For my old Perkins
4-107 to generate a respectable amount of amps it needs to be turning
about 1500 RPM.

Years ago I was up in Oklahoma looking at an oil field. A mile square
and wells about 100 yards apart and pumping jacks on every one of
those wells powered by one single cylinder diesel engine running on
crude oil that drove the pumps by pull rods running all over the
field.

I asked the Motorman how long the old engine had been running and he
told me that it was running when he was hired 15 years ago and had
never quit. The old engine had sat there for God only knows how many
years thundering along at 500 RPM. 20 years @ 24 hour/day = 175,200
hours........




Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)

Bruce in Bangkok wrote in
:

Years ago I was up in Oklahoma looking at an oil field. A mile square
and wells about 100 yards apart and pumping jacks on every one of
those wells powered by one single cylinder diesel engine running on
crude oil that drove the pumps by pull rods running all over the
field.


Put:
oil field diesel
into the YouTube search engine and you can watch them still running....lots
of them....