Engine Temperature Gauge Help Please.

[Wotname]

Please help me with finding a solution for fitting a meaningful engine water temperature gauge to my Yanmar 2GM20.

You would think this would be easy but…

The problem is the engine being raw water cooled runs with a cylinder head water temperature of around 55-60 C. The thermostat starts to open at 50 C and is fully open at 60 C.

All the marine and auto off-the-shelf electric gages that I can find operate from 40 to 120 C with the meaningful arc of the gauge around 80 to 100 C.

The reason for fitting the gauge is to monitor the thermostat operation as I have recently discovered my old thermostat was faulty (stuck half way open). The failed thermostat gave no external indication of a problem and so there is no way of knowing when the problem may occur again without physically removing the thermostat and eye balling it.

Thus I really need the meaningful arc of the gauge to be say 50 to 70 (or 80) C.

I can't think of anyway to modify an off-the-shelf gauge and sender so does anyone know how to do this?

The only other solution is to build my own sender and gauge and after discarding thermocouple concepts because of the small range I'm looking for (a maximum range of say 40 C). Perhaps something like this https://learn.adafruit.com/tmp36-tem...-a-temp-sensor
might be suitable. It would not be difficult to arrange a suitable power supply (3.5 to 5 V) and some suitable voltmeter for the display. I'm thinking of putting the TMP 36 sensor inside a custom made brass/bronze sender and fitting just like a normal sender in the head water jacket.

Would fitting a off-the-shelf cylinder head temperature be a smarter move as the cylinder head temperature must mirror the water temperature to a fair degree?

But please, if anyone knows a simpler or better solution, please share you knowledge.

[GILow]

PM sent.


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[Snowpetrel]

Hi Wottie, I just ordered a engine watchdog TM 4 for my nanni. I plan to hook up one thermocouple to the head and the other to the exhaust elbow. Hopefully it will give me temp, alarms and a quick indication of raw water failure if the exhaust bend temp rises suddenly. Hope to have it hooked up next week when it arrives. I can let you know how it goes, $190 au seemed like a cheap and easy way to get some alarms. If it all works as planned you'd be welcome to have a look. Based at POW bay or Kettering at the moment. Cheers

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[Wotname]

Originally Posted by GILow

PM sent.


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Thanks

[Wotname]

Originally Posted by Snowpetrel

Hi Wottie, I just ordered a engine watchdog TM 4 for my nanni. I plan to hook up one thermocouple to the head and the other to the exhaust elbow. Hopefully it will give me temp, alarms and a quick indication of raw water failure if the exhaust bend temp rises suddenly. Hope to have it hooked up next week when it arrives. I can let you know how it goes, $190 au seemed like a cheap and easy way to get some alarms. If it all works as planned you'd be welcome to have a look. Based at POW bay or Kettering at the moment. Cheers

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Thanks, the TM stuff looks like it might do the job. I will read more tomorrow.
How long are you expecting to be in Kettering.

Off-the-shelf is better DIY

[Snowpetrel]

I'm normally based in Kettering on a mooring, but have the boat up at POW marina for the next week or so.

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[ex-12m-guy]

This unit may fill the bill. Gets decent reviews and the price is right:

Whoops. Looks like web address was truncated.

Search Amazon for this item "Buler Digital"

http://www.amazon.com/Buler-Digital

[bailsout]

My 2QM15 has a mechanical gauge that starts at 100F and it hs never left the mark. Raw water cooled by 55F seas. Gauge and thermostat check out on stovetop. Never run over 1500 rpm.

[deblen]

Wotname is looking for an analogue mechanical engine water temp gauge that displays a temp band from 40C to 80C.
That is 120F to 175F for us North American metric illiterates
I don't think he will find one,but here is a link:
Note: Google "Racing gauges,etc.

Water Temperature Gauge 52mm with audible Alarm - AMBER BACKLIT - www.roadrunneroffroad.com.au

I suggest an exhaust temp alarm also. I use one by Borel Mfg. The sensor clamps around the rubber exhaust hose & has an included wire & loud beeper.
Just provide +12V from "Ign" or whatever.

Next : Google Digital water temp gauges Australia. Got several hits including ebayAU for <$30--again racing gear.
The same in Marine will be several xx as much per usual.

There are also "self powered" cyl head temp gauges for small engines-bikes,atv's,snowmobiles,etc that have a sensor that goes under a headbolt,or whatever, & no ext. pwr reqd.

A water temp sensor (Mech. or Electric)must go into the water in the water passage or hose. It will not be meaningful if you just tee it,like you can with a oil pressure gauge. This means finding an extra tapped hole into water jacket,or replace existing electric sensor with a mech. one. Mech. sensors typically have a longer sense element than electric senders.This means you need enough depth in the water jacket to accommodate it,without it hitting the "back of the hole" & touching the interior surface.or..worse.
Most sensors are standard NPT national pipe TAPER & I believe BNPT/BSPT? British TAPER thread is compatible.Stay away from NP Straight or British equiv.-they are meant for seacocks & other special situations & do not seal by simple tightening.

Hope this helps
Cheers/Len

[chiefcoxswain]

can not go past Engine Watch dog, have one fitted to Ford Lehman 120 with Siren and digital display, temp goes up as engine warms up and an alarm will sound when temp reaches pre set " over desired temp level" also have one fitted to four wheel drive vehicle. Engine watch dog Aust $ 130 Siren EBay Aust $20. Wiring diagram supplied.

[n8kraft]

I had my engine temp gage stop working so I just got a laser temperature gun and shot the elbow coming in to the heat exchanger hourly. Total cost, $30 but not an immediate shutdown system in case your engine cooling system stops working.

[Stu Jackson]

Originally Posted by Wotname

But please, if anyone knows a simpler or better solution, please share you knowledge.

Buy four thermostats.

Change them every other year.

Seriously.

[Shawn67]

Some old VDO gauges went to 100c degrees and had likely enough useful arc to tell your temp on a raw water engine. If you can find the correct sender to go with it.

Stewart Warner 82114 would work as well. 150 degrees F is straight up and you have gauge movement by around 120 degrees. Use sender 280EA. I recently put one of them in my Volvo MD7A that I converted to fresh water cooling. The old gauge in the volvo was full scale around 140 degrees but it didn't have temp markings, just a cold/hot scale.

Shawn

[Shawn67]

"The old gauge in the volvo was full scale around 140 degrees but it didn't have temp markings, just a cold/hot scale."

BTW, that old gauge was a weird setup. The sender was VDO but the gauge itself was a Stewart Warner. I initially used the VDO sender with the newer Stewart Warner 82114 and it went full scale around 140 degrees too. Swapping out to the proper 280EA sender made the gauge agree with my IR thermostat. If you were willing to make a custom gauge face you could likely use a Stewart Warner gauge with a VDO sender to get what you are looking for.

Shawn

[Cap Erict3]

Originally Posted by Stu Jackson

Buy four thermostats.

Change them every other year.

Seriously.

Best advice given. Thermostats are bimetallic and are a very dependable component of an engine.

Adding a high temp alarm would be worthwhile.


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