Yanmar 2gm20f temp creeping up

[wmcunninghamii]

OK, I went down to the boat and did a bit of a deep dive into the two two Yanmar technical Documents I possess

Doc #1 = The Basic Ops manual that came with the engine (multiple languages NOT user friendly)

and

Doc #2 = The Yanmar Shop Manual which covers the 1gm10, 2gm20 and 3gm30

The first and most annoying point is that neither of them explicitly says "the normal operating temperature range for the engine is XXX to XXX)

The Basic ops manual contains a table that says:

"Thermostat Open - begins to open 42C (109F) full open 52C (129F)"

that seems very low to me.

This document further states:

(5) Temperature of parts

"under full power the temperature of each engine part will be about 50 to 60C or slightly hot if touched by the hand... if the temp is too high there is some abnormality..."

This is a dummy light in print and pretty much useless info IMO

Shop Manual - Freshwater cooled engine - 2GM20F section

"Thermostat operating Temperature

opening temp 71C (159.8F)

full open temp 85C (185F)


Cooling water temp switch (aka alarm switch)

ON 95C (202-193 F)

OFF 88C (187F ) or higher " (what the heck does this mean, shouldn't that read "or lower"?)

So neither doc states the actual expected operating temperature range for any of the documented engines. And the basic ops doc just seems flat out WRONG. However there appear to be errors in both docs.

I have to assume the Shop Manual is correct, or, at least, more correct. If so, then I am worrying about nothing. Heck, the thermostat is just opening at the temps I am seeing and the reason I am worried is because of the statements in the Basic operation manual which imply anything more than about 60C (140F) is bad. If the shop manual is correct then a64pilot is right on the money with respect to the thermostat just starting to open at the temps I am seeing.

Does anyone have an ops temp spec for the 2GM20F that can be traced back to a specific technical document from Yanmar? One that can be trusted to be correct?

[wmcunninghamii]

Also found an outstanding review of Yanmar (and other) thermostat operation with diagrams on this forum.

https://www.cruisersforum.com/forums...em-122461.html

[wmcunninghamii]

OK, I have found an additional resource online which appears to be an extract from yet another Yanmar technical document. It appears to be an extract from the shop manual but a different version from the one I possess.

This doc contains this table and, perhaps clarifies the disconnect between my two docs.

My basic operator manual seems to refer to the Raw Water cooled engine while the shop manual refers to the fresh water cooled engine.

It is interesting the fresh water cooled thermostat spec is so different from raw water version.

[CAR54]

About two years after making the transition from the Chesapeake to Lake Ontario fresh water the high temperature sounded on my 2gm20f. After trouble shooting found there is a 90 degree brass fitting on the top the engine cooling system that had caked heavily with rust particles, cleaned it out and changed all cooling hoses. Its been fine ever since. I asked the people at Niemic marine Yamar parts dealer if they ever heard of this problem and they said "no". I average about 50 - 100 hours a year on the engine and maintain a ships and engine log for tracking purposes.

[Wotname]

Originally Posted by wmcunninghamii

.......

My basic operator manual seems to refer to the Raw Water cooled engine while the shop manual refers to the fresh water cooled engine.

It is interesting the fresh water cooled thermostat spec is so different from raw water version.

Raw water directly cooled engines must be operated at much lower temperatures than coolant cooled engines.

This is because salts from the sea water (mainly calcium carbonate) are deposited into the engine water galleries at temperatures above about 50C.

[kaisardog]

While you are working on the heat exchanger you might as well clean and flush the coolant. These 2 gm20f s are very sensitive to dirty coolant or insufficient levels in the overflow tank.
You might find that a simple coolant flush and replacement w the proper coolant solves yr problem. If not i d go to the heat exchanger cleanout next. And if you.re doing the He cleanout remeber you will need an extra of its little weird yanmar gasket , or plan to use formagasket and hope it doesn.t suck into oneof the cooling tubes. As to themix el replacement check a yanmar parts manual — as i recall the mix el is reverse threaded. And expensive....

[wmcunninghamii]

again, thanks all for the excellent suggestions and feedback. I definitely understand more about the RW cooled and FW cooled engines now.

The reason for the cooler running RW cooled engine is now much clearer.

I am sorry to beat a dead horse but someone mentioned running the engine at cooler temperatures was a bad thing But if the FW engine is run at the same temp as the RW engine, meaning it would be run colder than spec for the FW unit, then how could that cause damage? Is the Raw Water cooled engine designed or constructed differently to accommodate the lower operating temps?

[wmcunninghamii]

Originally Posted by kaisardog

While you are working on the heat exchanger you might as well clean and flush the coolant. These 2 gm20f s are very sensitive to dirty coolant or insufficient levels in the overflow tank.
You might find that a simple coolant flush and replacement w the proper coolant solves yr problem. If not i d go to the heat exchanger cleanout next. And if you.re doing the He cleanout remeber you will need an extra of its little weird yanmar gasket , or plan to use formagasket and hope it doesn.t suck into oneof the cooling tubes. As to themix el replacement check a yanmar parts manual — as i recall the mix el is reverse threaded. And expensive....

I am pretty good about my routine coolant replacement. I comply with the Yanmar recommended periodicity and just recently did a coolant change. However I did not quite a bit of sludge on the tube assembly case which is visible from the cap opening. So a good cleaning is probably overdue. I am aware of that pesky gasket and have one or two in my spares kit.

One other thing I did not realize and came to understand after my shop manual deep dive is that the raw water actually circulates back and forth through the heat exchanger core. I believe it does three transits. I had always envisioned the water going in one end and out the other in a straight line flow.

[wmcunninghamii]

Originally Posted by CAR54

About two years after making the transition from the Chesapeake to Lake Ontario fresh water the high temperature sounded on my 2gm20f. After trouble shooting found there is a 90 degree brass fitting on the top the engine cooling system that had caked heavily with rust particles, cleaned it out and changed all cooling hoses. Its been fine ever since. I asked the people at Niemic marine Yamar parts dealer if they ever heard of this problem and they said "no". I average about 50 - 100 hours a year on the engine and maintain a ships and engine log for tracking purposes.

Good tip. I will have a look at that if necessary. I am headed out for a trip next week and plan to observe temps very carefully. As I mentioned earlier, I may have been running cold for a long time and not realized. But this small L is yet another thing I will bear in mind if further troubleshooting is necessary.

[kaisardog]

Originally Posted by wmcunninghamii

again, thanks all for the excellent suggestions and feedback. I definitely understand more about the RW cooled and FW cooled engines now.

The reason for the cooler running RW cooled engine is now much clearer.

I am sorry to beat a dead horse but someone mentioned running the engine at cooler temperatures was a bad thing But if the FW engine is run at the same temp as the RW engine, meaning it would be run colder than spec for the FW unit, then how could that cause damage? Is the Raw Water cooled engine designed or constructed differently to accommodate the lower operating temps?

don't run yans at too cool a temp. worst thing you can do is baby them runnign at idle a couple hrs a month just to get in and out of your slip. the safest thing to do is check yr parts book for the correct temp of thermostat for your particular model, keep it in place, and carry an extra. the thermostat is fail-open as i recall. per mack boring yan east coast distributor advanced engine course, you don't want to run a yan 'cool' they need to be run 'hot and hard' at least an hour every couple weeks. 'it blows the carbon out.' a yanmar gold dealer like niemec will sell you the right thermostat for your engine -- and while u r at it get the parts manual for your engine. it is invaluable as it shows blowup assembly diagrams w the bolt sizes, thread directions, pitch etc.

[wmcunninghamii]

Originally Posted by kaisardog

don't run yans at too cool a temp. worst thing you can do is baby them runnign at idle a couple hrs a month just to get in and out of your slip. the safest thing to do is check yr parts book for the correct temp of thermostat for your particular model, keep it in place, and carry an extra. the thermostat is fail-open as i recall. per mack boring yan east coast distributor advanced engine course, you don't want to run a yan 'cool' they need to be run 'hot and hard' at least an hour every couple weeks. 'it blows the carbon out.' a yanmar gold dealer like niemec will sell you the right thermostat for your engine -- and while u r at it get the parts manual for your engine. it is invaluable as it shows blowup assembly diagrams w the bolt sizes, thread directions, pitch etc.

I have the parts and shop manuals. They are indeed invaluable.

Based upon my low ops temp - around 150 to 160 on my FW cooled engine I think you may have identified my problem. I thought I was running hot as I got above my normal 150 degree ops temp. What I believe may be happening is the thermostat has failed open. I am running in warm water/weather so the engine may be heating up a bit more than I am used to, but what I am used to is not the correct ops temp! The other possibility is that I inadvertently replaced the thermostat with the wrong part (for RW cooled) years ago.
UH OH!

I need to check this out!!

Unfortunately, until I began this thread and started hearing from some of you, I did not realize there was a big difference in ops temps between FW and RW cooled engines. I have had the wrong number in my mind for years.I partly blame the manuals which are not explicit about this, you have to dig around
... or ask this board. Obviously I am late to both.

[Compass790]

Originally Posted by wmcunninghamii

I have the parts and shop manuals. They are indeed invaluable.

Based upon my low ops temp - around 150 to 160 on my FW cooled engine I think you may have identified my problem. I thought I was running hot as I got above my normal 150 degree ops temp. What I believe may be happening is the thermostat has failed open. I am running in warm water/weather so the engine may be heating up a bit more than I am used to, but what I am used to is not the correct ops temp! The other possibility is that I inadvertently replaced the thermostat with the wrong part (for RW cooled) years ago.
UH OH!

I need to check this out!!

Unfortunately, until I began this thread and started hearing from some of you, I did not realize there was a big difference in ops temps between FW and RW cooled engines. I have had the wrong number in my mind for years.I partly blame the manuals which are not explicit about this, you have to dig around
... or ask this board. Obviously I am late to both.

Thanks a lot for posting Andrew Troups excellent thread explaining how they work.
Please post back what you find after you test the thermostat.
It does say in our raw water Yanmar ysm8 manual to test the thermostat periodically but if you keep an eye on the engine temps you should know when it is not working.
Better to run at fresh water cooled temp than raw water cooled if you have a fresh water cooled engine for engine efficiency & oil cleanliness reasons.

[Wotname]

Originally Posted by wmcunninghamii

.....

I am sorry to beat a dead horse but someone mentioned running the engine at cooler temperatures was a bad thing But if the FW engine is run at the same temp as the RW engine, meaning it would be run colder than spec for the FW unit, then how could that cause damage? Is the Raw Water cooled engine designed or constructed differently to accommodate the lower operating temps?

Do not confuse the coolant (either FW or RW) temperature with the combustion/exhaust gas temperature.

You can run a RW engine hard and hot enough to keep "the insides clean" i.e. prevent carbon build up.

As far as the Yanmar GM series of engines goes, there is no difference in the basic design or construction between the FW or RW engines. They were all initially designed operate on RW. The FW version simply has the addition of the necessary cooling system components.

[Compass790]

Doc #2 = The Yanmar Shop Manual which covers the 1gm10, 2gm20 and 3gm30

The first and most annoying point is that neither of them explicitly says "the normal operating temperature range for the engine is XXX to XXX)

The Basic ops manual contains a table that says:

"Thermostat Open - begins to open 42C (109F) full open 52C (129F)"

that seems very low to me.

This document further states:

(5) Temperature of parts

"under full power the temperature of each engine part will be about 50 to 60C or slightly hot if touched by the hand... if the temp is too high there is some abnormality..."

This is a dummy light in print and pretty much useless info IMO

This is telling you that that if you point an infrared thermometer at the engine block on a raw-water cooled engine it should not be hotter than 60oC

Shop Manual - Freshwater cooled engine - 2GM20F section

"Thermostat operating Temperature

opening temp 71C (159.8F)

full open temp 85C (185F)

This is telling you that on a fresh water cooled engine at operating temp if you point your thermometer at the block it should be at least 85oC



Cooling water temp switch (aka alarm switch)

ON 95C (202-193 F)

OFF 88C (187F ) or higher " (what the heck does this mean, shouldn't that read "or lower"?)

Yes I agree that should read " or lower " It's not the only mistake I've seen in a service manual

So neither doc states the actuall expected operating temperature range for any of the documented engines. And the basic ops doc just seems flat out WRONG. However there appear to be errors in both docs.

I have to assume the Shop Manual is correct, or, at least, more correct. If so, then I am worrying about nothing. Heck, the thermostat is just opening at the temps I am seeing and the reason I am worried is because of the statements in the Basic operation manual which imply anything more than about 60C (140F) is bad. If the shop manual is correct then a64pilot is right on the money with respect to the thermostat just starting to open at the temps I am seeing.

Does anyone have an ops temp spec for the 2GM20F that can be traced back to a specific technical document from Yanmar? One that can be trusted to be correct?[/QUOTE]

Yes Wotname has a good point that you shouldnt confuse exhaust gas temperature with block temps.
You are better off with the fresh water thermostat in an FW engine as it will warm up faster & boil the condensates out of the oil faster. Reduces cold oil drag as well so helping efficiency.
Especially important if you only do short runs although I guess you motor a bit being at Discovery bay

[wmcunninghamii]

Originally Posted by Compass790

Doc #2 = The Yanmar Shop Manual which covers the 1gm10, 2gm20 and 3gm30

The first and most annoying point is that neither of them explicitly says "the normal operating temperature range for the engine is XXX to XXX)

The Basic ops manual contains a table that says:

"Thermostat Open - begins to open 42C (109F) full open 52C (129F)"

that seems very low to me.

This document further states:

(5) Temperature of parts

"under full power the temperature of each engine part will be about 50 to 60C or slightly hot if touched by the hand... if the temp is too high there is some abnormality..."

This is a dummy light in print and pretty much useless info IMO

This is telling you that that if you point an infrared thermometer at the engine block on a raw-water cooled engine it should not be hotter than 60oC

Shop Manual - Freshwater cooled engine - 2GM20F section

"Thermostat operating Temperature

opening temp 71C (159.8F)

full open temp 85C (185F)

This is telling you that on a fresh water cooled engine at operating temp if you point your thermometer at the block it should be at least 85oC



Cooling water temp switch (aka alarm switch)

ON 95C (202-193 F)

OFF 88C (187F ) or higher " (what the heck does this mean, shouldn't that read "or lower"?)

Yes I agree that should read " or lower " It's not the only mistake I've seen in a service manual

So neither doc states the actuall expected operating temperature range for any of the documented engines. And the basic ops doc just seems flat out WRONG. However there appear to be errors in both docs.

I have to assume the Shop Manual is correct, or, at least, more correct. If so, then I am worrying about nothing. Heck, the thermostat is just opening at the temps I am seeing and the reason I am worried is because of the statements in the Basic operation manual which imply anything more than about 60C (140F) is bad. If the shop manual is correct then a64pilot is right on the money with respect to the thermostat just starting to open at the temps I am seeing.

Does anyone have an ops temp spec for the 2GM20F that can be traced back to a specific technical document from Yanmar? One that can be trusted to be correct?

Yes Wotname has a good point that you shouldnt confuse exhaust gas temperature with block temps.
You are better off with the fresh water thermostat in an FW engine as it will warm up faster & boil the condensates out of the oil faster. Reduces cold oil drag as well so helping efficiency.
Especially important if you only do short runs although I guess you motor a bit being at Discovery bay[/QUOTE]


Thank you for the clarifications. When I point my infrared gun at the block I see about 148 - 155 F (65C +/-) after warm up under load (2500 RPM) so it appears I am running cold by about 25 degrees F +/-. yikes, I need to get this fixed. Goodness knows how long I have been running at these temps... 10 or 15 years.

Yes, I do a lot of motoring to get out to sailable water and I will often motor all the way to the Bay, a 10 to 12 hour trip in my boat. The engine has about 1600 hours at this point. Actually not too bad for a 33 year old engine I guess. I have about 21K NM in my log so maybe 15- 20% motoring. Although 140 hours of that was motoring through the Pac High coming back from Hawaii, so I have an excuse. Some of the hours were accumulated by the previous owner who did not keep a log, there is no meter, I bought the boat at 13 years old. I simply used my annual average and attributed a similar annual number to the PO so the total hours are an estimate with capital E. Also some hours have been charging only during my ownership. Bottom line, I have done a lot of motoring at low temp , some of it unloaded.

I could be arrested for engine abuse.