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Old 05-15-2015, 11:43 PM   #1
Join Date: Apr 2009
Posts: 14
nmea2000 and engine instruments

Hi all,
I'm trying to sort out why my brand new garmin 547 xs reads my brand new tohatsu engine temperature 50 degrees F hotter than it actually is (according to my infra-red heat gun).

Specifically the garmin says my cooling water temperature is 175 degrees F when my heat gun says it is 125 to 128 degrees F.

I have the honda/tohatsu factory service manual but it does not give any real detail on sensor parameters and this is a new motor so I should not be taking it apart to trouble shoot it.

I'm new to nmea2000 networks so I'm trying to figure out if this is a sensor issue, a network issue, or a garmin issue.

Does anybody have direct experience in this sort of stuff?

I want to know what is happening so I don't get stuck in the loop where tohatsu says it is a garmin problem and garmin says it is a tohatsu problem


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Old 05-16-2015, 10:16 AM   #2
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Sounds like a Thohatsu problem, although have you check if they're are any temp offsets in the garmin unit itself? I have a E-tec and the temp reads normal on my 441s.

Thanks, Oliver
M/V Oliver
Nordhavn 47 Hull #12
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Old 05-16-2015, 11:07 AM   #3
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The Garmin temperature for the engine sounds right at 175 degrees but the gun at 125 degrees sounds really low. Our Perkins runs about 175-180 degrees.
Mike Barge
MV Rochepoint
Sidney, British Columbia.
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Old 05-16-2015, 08:35 PM   #4
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City: Gloucester, MA
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It's probably just the difference between the temp of the coolant/water inside the engine, and the spot where you are measuring. 175F sounds right on for coolant temp around the internals of the engine. You are probably just measuring an extremity where it's cooler.

Where are you measuring with the heat gun? And are you in real close? The measurement cone on those guns spreads out really fast. There is usually a little diagram on the gun to show how big the sense area is at any given distance. The little laser dot is VERY misleading.

It sounds to me like everything is working just fine.
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