Convert Idiot Light to Thermostat Gauge?

VT Fitz

VT Fitz

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Oct 19, 2006
337
Hunter 27-3 Brownsville, VT/Mystic, CT
On my ‘07 Hunter 27 with a Yanmar 2YM15, I don’t have a thermostat, just an idiot light on the instrument panel. My exhaust manifold/heat exchanger just broke due to extreme corrosion (a sad tale not worth telling here, but I will share I was shocked by how clogged the piece was), and I have the replacement kit on the way from HDI Marine in Vancouver, Washington. That’s all good.

However, it got me thinking it would be a good idea to have an actual temperature gauge, not just an overheating warning light. I’m not eager to run a new wire from the instrument panel to the engine compartment. Does anyone know if I can take the wiring going to the warning light and switch it over to a gauge?

Thanks for any advice.
 
JoeWhite

JoeWhite

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Mar 6, 2008
1,341
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
Yes you can as long as you have a grounding point on the instrument panel.
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,262
Hunter 310 West Vancouver, B.C.
VT Fitz said:
Does anyone know if I can take the wiring going to the warning light and switch it over to a gauge?
Click to expand
Not a good idea, in fact a terrible idea. If you go over temp. for any reason (a failed raw water pump perhaps) you want a screaming hi temp. alarm to draw your attention to the problem. With only a gauge, you may not notice an overheating problem for hours. Come to think of it, a seized engine would notify you quite promptly if you are overheating :yikes:.

VT Fitz said:
I’m not eager to run a new wire from the instrument panel to the engine compartment.
Click to expand
This is really not as bad as you might think. I managed to go down through the bottom of the binnacle with a waterproof cable gland to ensure no water got through to the ceiling liner below.

1700199356954.png


From there just followed through to a good sensing point. None on the engine so I used one of the engine coolant hoses to the hot water tank. Because it's in a non conducting hose, you have to make up the ground.

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1700199910151.jpeg
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,140
CAL 35 Cruiser #21 moored EVERETT WA
VT Fitz said:
take the wiring going to the warning light and switch it over to a gauge
Click to expand
Breaking this query down to simplest terms.
  1. Wire - yes the wire can be used for a temp switch signal (what you have now) or a temp gauge signal (what you desire)
  2. Gauge, the instrument that displays the temperature, you will need to acquire and install this on your panel. They have certain requirements as to signal they receive from the sensor installed on your engine
  3. Sensor, you will need to acquire and install a temp sensor on the engine or in a hose that contains the coolant from the engine (as Ralph indicates). On engine sensors provide more accurate indication of the engine temperature.
 
rgranger

rgranger

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Jan 19, 2010
12,565
Hobie 16 & Rhodes 22 Skeeter Charleston
Ralph Johnstone said:
Not a good idea, in fact a terrible idea. If you go over temp. for any reason (a failed raw water pump perhaps) you want a screaming hi temp. alarm to draw your attention to the problem. With only a gauge, you may not notice an overheating problem for hours.
Click to expand
I totaly understand that point... but I lost a car back in the early 90's .... the idiot light came on about 2 seconds before the engine siezed. ... Now I only buy cars that have a functioning gauge.

Maybe the best solution would be to have both a gauge and a warning buzzer. Or a gauge with a buzzer.:shhh:

That way you can see that things are "not normal" before they become a crisis.
 
Richard19068

Richard19068

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Jun 11, 2004
1,767
Oday 31 Redondo Beach
rgranger said:
Maybe the best solution would be to have both a gauge and a warning buzzer. Or a gauge with a buzzer.:shhh:

That way you can see that things are "not normal" before they become a crisis.
Click to expand
Yes. A gauge and a buzzer both.
My gauge and warning light are in an awkward place to see so I added a buzzer to the idiot light circuit.
Adds a lot of peace of mind.
 
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Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,262
Hunter 310 West Vancouver, B.C.
rgranger said:
Maybe the best solution would be to have both a gauge and a warning buzzer. Or a gauge with a buzzer.:shhh:
Click to expand
I completely agree BUT given a choice of only one which most people with boats have (audible alarm only) I'd take the alarm. And that's why I have both.
 
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Richard19068

Richard19068

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Jun 11, 2004
1,767
Oday 31 Redondo Beach
Ralph Johnstone said:
I completely agree BUT given a choice of only one which most people with boats have (audible alarm only) I'd take the alarm.
Click to expand
Agreed.
He already has a light so it should be quite easy to add an alarm on the same circuit.
The gauge would be nice but a little more involved installation.
 
VT Fitz

VT Fitz

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Oct 19, 2006
337
Hunter 27-3 Brownsville, VT/Mystic, CT
Thanks for all the input so far. Very helpful!

As far as "swapping" the idiot light for a gauge creating a potential it's-too-late scenario, truth is the panel on our boat is not at the helm but on the starboard coaming and is blocked from view most of the time. Even if someone isn't sitting in the way, it's not easy to see what's happening there. So if the light triggered, I'm not sure would notice it anyway, or at least not immediately since I'm not normally focussed on that area.

With all the food for thought you've provided, you got me thinking that if I do indeed use the wiring to the warning light to put a gauge on the instrument panel, I should install an idiot light on the binnacle next to my chart plotter, which is an area I do look at regularly. The cable path from there to the engine compartment is much easier than from the starboard coaming.
 
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Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,262
Hunter 310 West Vancouver, B.C.
VT Fitz said:
I should install an idiot light on the binnacle next to my chart plotter, which is an area I do look at regularly.
Click to expand
Rather than just a light which shows what system is the problem, I have an alarm which is so loud and ungodly, you can't ignore it. Everything alarm switch on the engine is wired through the one audible alarm and then a glance around the cockpit will show the one light that's on which shows who is causing all the ruckus.
 
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JoeWhite

JoeWhite

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Mar 6, 2008
1,341
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
VT, if an audible alarm will help you, just install a 110 dB 12vdc soanalert across the idiot light and mount it inside the instrument panel. I guarantee you that you will hear it.
 
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B

Blitz

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Jul 10, 2007
708
Seidelmann 34 Atlantic Highlands, NJ
years ago I thought someone made a gauge that would alarm when it reached a set temperature. Not sure where though... not much help I know
 
rgranger

rgranger

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Jan 19, 2010
12,565
Hobie 16 & Rhodes 22 Skeeter Charleston
Blitz said:
years ago I thought someone made a gauge that would alarm when it reached a set temperature. Not sure where though... not much help I know
Click to expand
Google found this one..

2-Channel Dual Round Digital EGT or CHT Pyrometer Gauge Display

• Small Size ~ 2-1/16" (52 mm) Round• Max temperature "Peak hold" display capture capability• High set-point alarm LED with internal relay contact• °F/°C selectable•...
thesensorconnection.com thesensorconnection.com
 
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