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Old 03-11-2012, 07:22   #1
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2GM20F Temperatures

Does anyone know what the correct engine temperature should be on this engine?

Since I have no temp gauge, will be using an infrared laser to check the engine temp.

Should I be checking the heat exchanger or the block itself for the best check? I assume they should be about the same.

Thanks!
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Old 03-11-2012, 07:50   #2
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Re: 2GM20F Temperatures

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Originally Posted by kiltym View Post
Does anyone know what the correct engine temperature should be on this engine?

Since I have no temp gauge, will be using an infrared laser to check the engine temp.

Should I be checking the heat exchanger or the block itself for the best check? I assume they should be about the same.

Thanks!

I have a temperature gauge (and the same engine). My engine runs consistently at 160 degrees. I understand that's a little low but the mechanic assures me it's hot enough. Even running it up to red line, the temp doesn't vary, to the point that I wondered if it was really reading ...

until two days ago.

We were moving my boat to its new location, and a lot was going on ... and I forgot to open the seacock.

After we'd been underway a few minutes I looked at the exhaust -- and she wasn't pumping water! Since the engine is barely a year old and I had very recently changed the impeller, I realized -- the seacock was closed. I have just started doing that routinely and haven't put a hook by it yet for the keys ...

Looked at the temp gauge and it was up to 180. So I had multiple clues, passed the helm over to my friend, went below and opened the seacock, and within five minutes the temp was back down to 160.

Oh I take that back I have a 3ym, not 2. On my old engine, which had major overheat problems, I tried a laser heat gun and found that it was really hard to read the same spot each time. If you're going to go that route, I suggest that once you've found the hottest spot, which you can use the gun to do, you mark it, so you read the same spot each time.
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Old 03-11-2012, 08:16   #3
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Re: 2GM20F Temperatures

I would suggest you shoot at something like the thermostat housing. The heat exchanger is likely to be cooler than engine temp, and sections of the block may not have coolant in them. The thermostat housing is where the thermostat regulates the temperature from anyway.

Just a wild guess, that engine should run between 160F and 180F under load.
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Old 03-11-2012, 08:39   #4
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Re: 2GM20F Temperatures

It is certainly worth doing this even if you have a temperature guage to establish some baseline results.
I think most freshwater cooled diesels will be reasonably similar.
Maine sail has a great article on this:
Engine Temp Monitoring & Over Heating Baseline Assessment Photo Gallery by Compass Marine at pbase.com
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Old 03-11-2012, 08:45   #5
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Re: 2GM20F Temperatures

my 2qm20h runs at 130-140 f. they run cool, as per my yanmar dealer/distributor in san diego. i dont know running temps for fresh water cooled yannies, but i am sure your yannie man does.....
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Old 03-11-2012, 08:55   #6
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Re: 2GM20F Temperatures

I just shot my 3gm30f (same engine, one more cylinder) with an IR gun at wot rpm. Realize that water temps here in Oriental have nosedived recently and were in the mid to upper 50s.

The temperature at the water pump housing stabilized at about 180 after running 5 minutes at wot. It probably would have been 200 or so at normal summertime water temps.

The temp immediately dropped to 160 or so when I backed off to low cruise speed.

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Old 03-11-2012, 10:52   #7
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Re: 2GM20F Temperatures

It has been several years since I owned a 2GM20F, but it seems to me that it was suppose to run pretty warm with fresh water, like 185. They are made differently than the raw water cooled engines which are suppose to run much cooler. The best place to test the water temperature is where the sensor is located, right on top of the thermostat housing. You can pick up a sensor with a gauge to test it.
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Old 03-11-2012, 18:09   #8
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Re: 2GM20F Temperatures

To give you a picture....aim the gun at the intake line and then at the line leading to the exhaust elbow.....that will give you coolant temp and differential
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Old 03-11-2012, 18:39   #9
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Re: 2GM20F Temperatures

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Originally Posted by CCBullseye View Post
It has been several years since I owned a 2GM20F, but it seems to me that it was suppose to run pretty warm with fresh water, like 185. They are made differently than the raw water cooled engines which are suppose to run much cooler. The best place to test the water temperature is where the sensor is located, right on top of the thermostat housing. You can pick up a sensor with a gauge to test it.

Mine (new engine, only about a year old) has never run to 180 except the other day when I forgot to open the seacock. 160 is what I get consistently, all the time, at all RPM's. I've paid attention to it because I had such major overheat problems with the old engine... oy vey!
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Old 03-11-2012, 19:22   #10
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Re: 2GM20F Temperatures

Is the engine salt water cooled or freshwater cooled through a heat exchanger. If its salt water cooled, it should be run under 150 degrees to keep salt from cystalizing and blocking the cooling passages. A freshwater cooled engine should run hotter but probably less than 200 degrees
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Old 04-11-2012, 05:29   #11
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Re: 2GM20F Temperatures

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Originally Posted by Rakuflames View Post
Mine (new engine, only about a year old) has never run to 180 except the other day when I forgot to open the seacock. 160 is what I get consistently, all the time, at all RPM's. I've paid attention to it because I had such major overheat problems with the old engine... oy vey!
I appreciate the info but as you stated, you have a different engine.
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Old 04-11-2012, 05:31   #12
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Re: 2GM20F Temperatures

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Originally Posted by roverhi View Post
Is the engine salt water cooled or freshwater cooled through a heat exchanger. If its salt water cooled, it should be run under 150 degrees to keep salt from cystalizing and blocking the cooling passages. A freshwater cooled engine should run hotter but probably less than 200 degrees
It's freshwater cooled.

Thanks everyone for your responses, all helpful.
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Old 04-11-2012, 05:37   #13
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Re: 2GM20F Temperatures

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To give you a picture....aim the gun at the intake line and then at the line leading to the exhaust elbow.....that will give you coolant temp and differential
Intake line of the seawater or the coolant into the heat exchanger?

And what would this differential show me?

The hose leading to the elbow is the "warmed" sea water. If I measure the seawater intake it will tell me the temp difference but not sure what this value really tells me, except that some amout of heat is going out the exhaust.
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Old 04-11-2012, 06:25   #14
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Re: 2GM20F Temperatures

kiltym,

This may help you monitor both engines at the same time. Works great, been using them for a few years now.

Instruments
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Old 04-11-2012, 06:30   #15
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Re: 2GM20F Temperatures

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I appreciate the info but as you stated, you have a different engine.

Sorry, I thought we had the same one. I read 20, not 30.
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