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Old 07-01-2017, 09:51 AM   #1
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Lehman 120 temp GB 42 single diesel

Running across the albemarle sound today, quite bouncy. Temp going up above 200 @1800 rpm. Throttle back to 1500 and back down 180-190.

Both lower and upper helm agree.

What temperature should my Lehman 120 Run? Gonna troubleshoot tonight.

Kurt
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Old 07-01-2017, 10:15 AM   #2
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Sounds like its time to inspect all your engines coolant components-raw water impeller, coolant level, oil level, heat exchanger, etc. Don't forget the thermostat. Also, might want to get a reading on engine with a heat gun.
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Old 07-01-2017, 10:21 AM   #3
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3 simple things, depending on how bouncy at 1800 rpms, could have been sucking air into an intake, not likely but possible in teally rough conditions.

Second, could have sucked something up and it blocked some water flow.

3rd, could have pucked up a crab pot and the higher RPMs is making the engine work harder than the cooling system can cool....notice any black smoke?

Along with those possibles, then a methodic check of water flow is a good idea.
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Old 07-01-2017, 10:46 AM   #4
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Get a cheap IR heat gun. My temp gauges are way off. Bob Smith told me before he passed that the high temp alarm is the most accurate.

With the IR heat gun take several readings, as the angle humidity, and material can affect it.

HTH
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Old 07-01-2017, 02:45 PM   #5
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Temp that increases with load usually indicates restricted raw water flow.
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Old 07-02-2017, 08:13 PM   #6
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I took IR readings all over the engine and could not find over 140 degrees.

I had 140 at the water tank on the front of the engine.
I had like 113 on the valve cover.

I am underway tomorrow and will map out the temps so I can evaluate. For what it's worth, bother lower helm and upper helm agreed.

Regards,
Kurt
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Old 07-03-2017, 12:07 AM   #7
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Try testing at the sender location. That will tell you if the temp displayed is correct. Something has changed, what it it, and why.
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Old 07-03-2017, 07:20 AM   #8
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As you check temps with IR gun keep in mind it is coolant temperature that is critical for gauge comparison purposes. Raw water, valve cover or other points have their own curiosities and ranges.

BTW, to insure your IR gun is not deceiving you check against a spoon immersed in boiling water. Last but not least, check your gauge wiring and spray retightened ends with an electrical lube.
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Old 07-03-2017, 08:24 AM   #9
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I cleaned the raw water strainer while we were in Port. We are underway today and reading 180 at 1900 rpm. I checked block near temp sensor in two places and got a steady 170. The strainer did not look that clogged, but it appears to be better now. I got 8 hours of steaming today, we shall see. Thanks for all the replies.
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Old 07-03-2017, 04:18 PM   #10
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Quote:
Originally Posted by kurt.reynolds View Post
I took IR readings all over the engine and could not find over 140 degrees.

I had 140 at the water tank on the front of the engine.
I had like 113 on the valve cover.

I am underway tomorrow and will map out the temps so I can evaluate. For what it's worth, bother lower helm and upper helm agreed.

Regards,
Kurt
First. Pick a spot on your engine coolant tank and use that spot as your reference.
IR gun should be inches away for most accurate results.

How far above 200?
220 or 280 sorta makes a difference.
If i raise rpms from 1500 too 2000, I expect the temp to go up (It goes to 200 to 210) since at 15 to 1600 rpms I think the thermostat is the only thing keeping the temperature up. U
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Old 07-06-2017, 06:23 PM   #11
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So I have figured out it is the temperature gage on the flying bridge that is in error. I have done an IR Temp on the engine and verified the lower helm temp gage is right.

The Temp gage on the upper helm fluctates with RPM, turn on the instrument lighting and it jumps 20 degrees and reads consistently 15 degrees high at 1900 rpm steady cruising.

Now I need to decide what do do about my temperature instrumentation.

I am guessing there are a lot of options, will be investigating.

Thanks for all the thoughtful and insightful replies. You guys are the best.
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Old 07-06-2017, 06:58 PM   #12
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Greetings,
Mr. k. Sounds to me more like an electrical problem that is outside the gauge (ground, bad connection, high resistance connection...) rather than the internals of the gauge itself but that's just a guess. Any gauges I've ever had fail were either go or no go.
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Old 07-06-2017, 07:14 PM   #13
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Mr. K, Mr. RT usually make a pretty good guess. I guess.
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Old 07-06-2017, 07:54 PM   #14
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Quote:
Originally Posted by RT Firefly View Post
Greetings,
Mr. k. Sounds to me more like an electrical problem that is outside the gauge (ground, bad connection, high resistance connection...) rather than the internals of the gauge itself but that's just a guess. Any gauges I've ever had fail were either go or no go.
Second the motion that Mr. RT is correct. Temp gauges measure resistance, which means any resistance in the circuit counts. if the gauges haven't been replaced it's wiring, start with the ground path. If one has been replaced and the other hasn't... that will cause similar problems.

After chasing electrical gremlins for years I just gave up, I know the engine is 20 degrees cooler than the flybridge says, and I know the RPM is off. I'm on Lake Erie so TowBoat is never far away...
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Old 07-07-2017, 01:51 AM   #15
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Originally Posted by SeaMoose View Post

Second the motion that Mr. RT is correct. Temp gauges measure resistance, which means any resistance in the circuit counts. if the gauges haven't been replaced it's wiring, start with the ground path. If one has been replaced and the other hasn't... that will cause similar problems.

After chasing electrical gremlins for years I just gave up, I know the engine is 20 degrees cooler than the flybridge says, and I know the RPM is off. I'm on Lake Erie so TowBoat is never far away...
third the motion
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