On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:

On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:

Diesels don't have this problem, and so are less wasteful at low
revs.

That's true but they have maintenance issues if run at low speed/low
load for extended periods of time.

Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".

Not that I'm advocating idling your diesel for days and days but I do
wonder about the people who worry about letting the engine idle. I've
seen people that would hardly let the poor old thing cool down before
stop-cocking it, "because it is bad to let the engine run at low
load".

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

I have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

But what do I know?


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

"Bruce in Bangkok" wrote in message
...


Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".


My guess is that idling during smoke or lunch breaks does not constitute
running at low power for a long time. My understanding is that a diesel
engine is happiest running at a constant RPM under a load that represents
about 80 percent of the engines power rating ... either in HP or watts.

Another issue that enters the picture is if a turbocharger is used or not.

The operator's manual for the Volvo diesels in our larger boat recommends
running at 200 RPM below WOT for maximum engine efficiency.

Our other boat, (single engined 36' GB) has two engine speeds .... 1700 rpm
or Off.

Eisboch

Bruce in Bangkok wrote:
On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:

On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:

Diesels don't have this problem, and so are less wasteful at low
revs.
That's true but they have maintenance issues if run at low speed/low
load for extended periods of time.

Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".

Not that I'm advocating idling your diesel for days and days but I do
wonder about the people who worry about letting the engine idle. I've
seen people that would hardly let the poor old thing cool down before
stop-cocking it, "because it is bad to let the engine run at low
load".

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

I have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

The issue with my motor, the Yanmar 2QM15, is that it runs cold at low
RPM. I can verify this. It's amazing how long it stays cold with no
load. This would be bad for it, right?

Stephen

"Stephen Trapani" wrote in
message ...

The issue with my motor, the Yanmar 2QM15, is that it runs
cold at low
RPM. I can verify this. It's amazing how long it stays
cold with no
load. This would be bad for it, right?


Yes. That is the main reason to not let a diesel sit at idle
too long. Low temp AND lower oil pressure at idle. For
years truck diesels have had a 'high idle' setting ( either
by air or electric solenoid, manual cable, or lately via
computer) so they can run them at night while parked.


SBV

On Sun, 25 Nov 2007 08:11:30 -0800, Stephen Trapani
wrote:

Bruce in Bangkok wrote:
On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:

On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:

snipped

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

I have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

The issue with my motor, the Yanmar 2QM15, is that it runs cold at low
RPM. I can verify this. It's amazing how long it stays cold with no
load. This would be bad for it, right?

Stephen

If your engine runs cold put a thermostat in it. Your Yanmar should
warm up like any engine and stay the same temperature from then on.
Running an engine at a lower then designed temperature is not the way
to go.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Bruce in Bangkok wrote:
On Sun, 25 Nov 2007 08:11:30 -0800, Stephen Trapani
wrote:

Bruce in Bangkok wrote:
On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:

On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:

snipped
The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

I have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.
The issue with my motor, the Yanmar 2QM15, is that it runs cold at low
RPM. I can verify this. It's amazing how long it stays cold with no
load. This would be bad for it, right?

Stephen

If your engine runs cold put a thermostat in it. Your Yanmar should
warm up like any engine and stay the same temperature from then on.
Running an engine at a lower then designed temperature is not the way
to go.

Why didn't Yanmar put a thermostat in this engine? Is there any
disadvantage to having the thermostat?

Stephen

On Sun, 25 Nov 2007 17:49:19 -0800, Stephen Trapani
wrote:

Bruce in Bangkok wrote:
On Sun, 25 Nov 2007 08:11:30 -0800, Stephen Trapani
wrote:

Bruce in Bangkok wrote:
On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:

On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:

snipped
The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

I have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.
The issue with my motor, the Yanmar 2QM15, is that it runs cold at low
RPM. I can verify this. It's amazing how long it stays cold with no
load. This would be bad for it, right?

Stephen

If your engine runs cold put a thermostat in it. Your Yanmar should
warm up like any engine and stay the same temperature from then on.
Running an engine at a lower then designed temperature is not the way
to go.

Why didn't Yanmar put a thermostat in this engine? Is there any
disadvantage to having the thermostat?

Stephen

Well, I think that they did. At least the 2GM20 I owned had a
thermostat and the parts book shows two, a normal temperature one for
freshwater cooling and a low temperature one for salt water cooling.


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:


On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:


Diesels don't have this problem, and so are less wasteful at low
revs.


That's true but they have maintenance issues if run at low speed/low
load for extended periods of time.

Bruce said:
Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".

Not that I'm advocating idling your diesel for days and days but I do
wonder about the people who worry about letting the engine idle. I've
seen people that would hardly let the poor old thing cool down before
stop-cocking it, "because it is bad to let the engine run at low
load".

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

But what do I know?

Bruce-in-Bangkok

Bruce, I suspect that all this came about as there are different types
of diesels out there, and *some of them* surely cannot be safely idled
for long periods. I knew a few tow truck operators that drove ford
diesels that told me that if the engines were not equipped with
high-idle switches the engines consistently did not last that long (tow
trucks spend a lot of time at idle). On the other hand, guys that drove
some other brands of tow trucks said they didn't need the fast idle, the
engines lasted just fine. My Dodge/Cummins pickup truck owner's manual
says to avoid idle any longer than 3-5 minutes - kind of a bitch since I
spend half the day in traffic.
In boats we have some (mostly older now) slow-turning diesels that
can be run all year at low speeds without any harm. But I suspect that
most of the newer, lighter, fast turning diesels of recent vintage are
better off above idle.
One more thing... *most* people I've observed around here driving
their boats into the dockage area are idling anyway. By the time they
are docked the engine is already sufficiently cooled and needs no more
idling at the dock, yet they usually spend another five or ten minutes
wasting fuel.
Red

On Sun, 25 Nov 2007 20:10:41 -0500, Red wrote:

On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:


On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:


Diesels don't have this problem, and so are less wasteful at low
revs.


That's true but they have maintenance issues if run at low speed/low
load for extended periods of time.

Bruce said:
Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".

Not that I'm advocating idling your diesel for days and days but I do
wonder about the people who worry about letting the engine idle. I've
seen people that would hardly let the poor old thing cool down before
stop-cocking it, "because it is bad to let the engine run at low
load".

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

But what do I know?

Bruce-in-Bangkok

Bruce, I suspect that all this came about as there are different types
of diesels out there, and *some of them* surely cannot be safely idled
for long periods. I knew a few tow truck operators that drove ford
diesels that told me that if the engines were not equipped with
high-idle switches the engines consistently did not last that long (tow
trucks spend a lot of time at idle). On the other hand, guys that drove
some other brands of tow trucks said they didn't need the fast idle, the
engines lasted just fine. My Dodge/Cummins pickup truck owner's manual
says to avoid idle any longer than 3-5 minutes - kind of a bitch since I
spend half the day in traffic.
In boats we have some (mostly older now) slow-turning diesels that
can be run all year at low speeds without any harm. But I suspect that
most of the newer, lighter, fast turning diesels of recent vintage are
better off above idle.
One more thing... *most* people I've observed around here driving
their boats into the dockage area are idling anyway. By the time they
are docked the engine is already sufficiently cooled and needs no more
idling at the dock, yet they usually spend another five or ten minutes
wasting fuel.
Red


I suspect that you are correct. I recently set the governor on a
Gardner 6 cylinder that turned a roaring 1,000 at full throttle and
drove a 50 foot teak junk at 7 - 8 knots.

My personal thoughts about diesels is that if you idle them for days
and days it is not good. However some idling followed by running them
at rated speed is not harmful.

I may be wrong but I've been treating them that way for a lot of years
and they haven't complained yet =:-)
Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

"Bruce in Bangkok" wrote in message
...
On Sun, 25 Nov 2007 20:10:41 -0500, Red wrote:

On Sat, 24 Nov 2007 23:49:00 -0500, Wayne.B
wrote:


On Sat, 24 Nov 2007 22:12:41 -0600, Brian Whatcott
wrote:


Diesels don't have this problem, and so are less wasteful at low
revs.


That's true but they have maintenance issues if run at low speed/low
load for extended periods of time.

Bruce said:
Yes there "seems" to be that but mention of "it is bad to run the
engine at low poser" seems confined to the boating world. I've worked
many construction jobs where diesel engines were started in the
morning and shut down at the end of the day. During smoke breaks or
lunch they just sat there and idled. Cranes are a perfect example,
that spend most of their life at very low power settings.

Generator sets - I've never seen a gen set operating manual that said
"run this engine at high power settings".

Not that I'm advocating idling your diesel for days and days but I do
wonder about the people who worry about letting the engine idle. I've
seen people that would hardly let the poor old thing cool down before
stop-cocking it, "because it is bad to let the engine run at low
load".

The Perkins I have in the sail boat has a continuous rating of 3,000
RPM and for years I ran it at 1500 - 1800. When I overhauled it I
could see no evidence of abnormal wear or carbon or any other evidence
that slow running harmed anything.

have the feeling that someone once said "it's not a good idea to
idle a diesel for a long time" and as the message passed from dockie
to dockie it became an urban legend and now everyone is worried about
idling the engine.

But what do I know?

Bruce-in-Bangkok

Bruce, I suspect that all this came about as there are different types
of diesels out there, and *some of them* surely cannot be safely idled
for long periods. I knew a few tow truck operators that drove ford
diesels that told me that if the engines were not equipped with
high-idle switches the engines consistently did not last that long (tow
trucks spend a lot of time at idle). On the other hand, guys that drove
some other brands of tow trucks said they didn't need the fast idle, the
engines lasted just fine. My Dodge/Cummins pickup truck owner's manual
says to avoid idle any longer than 3-5 minutes - kind of a bitch since I
spend half the day in traffic.
In boats we have some (mostly older now) slow-turning diesels that
can be run all year at low speeds without any harm. But I suspect that
most of the newer, lighter, fast turning diesels of recent vintage are
better off above idle.
One more thing... *most* people I've observed around here driving
their boats into the dockage area are idling anyway. By the time they
are docked the engine is already sufficiently cooled and needs no more
idling at the dock, yet they usually spend another five or ten minutes
wasting fuel.
Red


I suspect that you are correct. I recently set the governor on a
Gardner 6 cylinder that turned a roaring 1,000 at full throttle and
drove a 50 foot teak junk at 7 - 8 knots.

My personal thoughts about diesels is that if you idle them for days
and days it is not good. However some idling followed by running them
at rated speed is not harmful.

I may be wrong but I've been treating them that way for a lot of years
and they haven't complained yet =:-)
Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Okay, so it's been educational reading this thread.

It'll be another couple months to go, but I imagine Dad and I will do some
experimenting with fuel consumption in the GB42, with both engines throttled
back & one enging at a time shut down (probably alternating every couple
hours). Any ideas of where to look for appropriate fuel flow meters for
these?

I have another question, that's been brought up by reading this thread. My
own boat (GS41) has a Perkins 4-108. I have always been redicent to operate
it more than say 1350. What would the safe operating RPM be for this
engine? Reasonable cruising RPM?

Thanks!

Glenn.
s/v Seawing.