Need help with water temp sensor install on Yanmar 3YM30

[Madehn]

i don't think i can do a better job than the previous post explaining - i understand what your looking for but the temp gauge is not going to give it to you for an "instant reading"-- in the aircraft that i flew we had an EGT (exhaust gas temp) gauge or a turbine temp gauge that did give you real time info BUT if you started pushing the EGT you ran the risk of destroying the engine QUICK-- also had CHT or cylinder head temp gauges that gave you a very quick read- the majority of the time what i would want in a boat is an alarm that sounds before critical components start to melt- thus the exhaust temp gauge that i recommended. i do get your wanting to find the sweet spot for your engine etc. knowing how tough diesels are, i would tend towards a fuel flow meter so that i could see fuel flow versus speed and judge if i was getting anything extra out of pushing the throttle up another few hundred RPMs. i did look at these for my boat but finding one that could read low enough numbers (and i have a large diesel) that was reasonable dollar wise was tough. i finally decided that the juice was not worth the squeeze for me. best of luck - let us know how it turns out- i am always willing to learn from someone else's good ideas.

[Nani Kai]

Originally Posted by Wotname

Nani Kai, let's review engine cooling 101 and apologies if I am posting stuff you already know.

TL-DR - gauge only tells you if the coolant is too hot, it doesn't detect cooling defects that can catastrophically impact the exhaust system.

The temperature gauge only measure the coolant temperature and this is the last thing to change if a cooling fault develops. The coolant temperature is dependent of the thermostat, the coolant pump and the raw water (RW) cooling system. There is a fair amount of hysteresis in the total system, i.e. a delay between an issue and the response of the temperature gauge.

The coolant temperature should never exceed the fully open thermostat setting i.e. even when running at max rpm continuously, the temperature should remain constant at or below the thermostat rating. If the temperature starts to rise above the thermostat rating, there is an defect somewhere in the cooling system (coolant or RWC).

If you are using the temperature gauge to detect cooling faults, the following aspects should be noted.

1. Slowly developing issues (e.g. partially blocked heat exchanger or worn RW pump etc) will first show up (i.e. temperature rising above thermostat rating)
when operating at max rpm. At lower power settings, the temperature will remain normal until the defect gets worse (usually it has to get much worse).

2. Rapidly developing issues (e.g. blocked RW inlet) will not be detected by the gauge until after other serious problems develop - for instance exhaust system failure (burnt exhaust pipe / melted watercock etc).

So yes, an engine coolant temperature gauge is a handy tool to have and can help to detect slowing trending cooling system faults but won't detect rapidly occurring faults that might destroy the exhaust system.

IMO, the best (and still simple) arrangement is a coolant temperature gauge AND an exhaust temperature alarm.

While there are several types of exhaust temperature alarms, the Vetus one is probably the easiest (but not the cheapest) to install. Of course, an exhaust temperature alarm won't detect all slowly developing cooling faults, you need a gauge for that ()

https://www.vetus.com/en/exhaust-sys...struments.html

Mahlo Wotname for the detailed info. I appreciate that you gave the Coolant 101 explanation because it did provide info I did not previously know. If I understand everything correctly, it seems the best solution is to remove the coolant alarm sensor that incites the warning light, install the temp gauge sensor where the alarm sensor was and then add an exhaust temperature alarm per previous recommendations. This should give me the quickest and best "temperature critical" alarm and also deliver the cooling system data I want.

Have I missed anything?

[Nani Kai]

Originally Posted by Madehn

i don't think i can do a better job than the previous post explaining - i understand what your looking for but the temp gauge is not going to give it to you for an "instant reading"-- in the aircraft that i flew we had an EGT (exhaust gas temp) gauge or a turbine temp gauge that did give you real time info BUT if you started pushing the EGT you ran the risk of destroying the engine QUICK-- also had CHT or cylinder head temp gauges that gave you a very quick read- the majority of the time what i would want in a boat is an alarm that sounds before critical components start to melt- thus the exhaust temp gauge that i recommended. i do get your wanting to find the sweet spot for your engine etc. knowing how tough diesels are, i would tend towards a fuel flow meter so that i could see fuel flow versus speed and judge if i was getting anything extra out of pushing the throttle up another few hundred RPMs. i did look at these for my boat but finding one that could read low enough numbers (and i have a large diesel) that was reasonable dollar wise was tough. i finally decided that the juice was not worth the squeeze for me. best of luck - let us know how it turns out- i am always willing to learn from someone else's good ideas.

Thanks. I have a clearer understanding now, or at least have convinced myself that I do. My response to Wotname describes my plan going forward. I will post the results of the installations once complete and tested. Aloha

[Nani Kai]

Originally Posted by Madehn

i know you already have your equipment, but they make a sensor that goes on the outside of the exhaust that sounds a loud buzzer when the exhaust heats up too much ( loss of cooling water flow) but prior to meltdown- put one on my engine in less than hour including running lines to the binnacle for the buzzer/siren. very easy and just as useful.

Do you have info on brand/part number or any other information that might help me locate this? At this point I am leaning toward installing both an exhaust temperature alarm and a coolant temperature gauge. Thanks for any info you can provide.

[Wotname]

^^ Snap Disc or snap action thermostats.

See https://www.comstatinc.com/thermostats/snap-disk
and for more info see https://www.google.com/search?client...sclient=psy-ab

[Wotname]

Originally Posted by Nani Kai

Mahlo Wotname for the detailed info. I appreciate that you gave the Coolant 101 explanation because it did provide info I did not previously know. If I understand everything correctly, it seems the best solution is to remove the coolant alarm sensor that incites the warning light, install the temp gauge sensor where the alarm sensor was and then add an exhaust temperature alarm per previous recommendations. This should give me the quickest and best "temperature critical" alarm and also deliver the cooling system data I want.

Have I missed anything?

I wouldn't recommend removing the existing warning light / alarm components, especially if there is no need to do it. I would first check out the "green circled plug" mentioned upthread.

While an engine coolant defect is unusual, it is possible to an engine overheat to occur even when the raw water circuit is operating normally. The existing light / alarm is the last line of defence in such a situation.

Maybe I just a 'belt and braces' man .

[Davo1404]

This is the far simpler solution. I have one on my Yanmar 2gm20f. One probe hose clipped to the exhaust elbow just below the water injection. The other probe is placed under a bolt on the thermostat. Excellent device with manual settings.

https://engineguard.com.au/

[Wotname]

Originally Posted by Davo1404

This is the far simpler solution. I have one on my Yanmar 2gm20f. One probe hose clipped to the exhaust elbow just below the water injection. The other probe is placed under a bolt on the thermostat. Excellent device with manual settings.

https://engineguard.com.au/

Very true. Engine Watchdog is pretty good too. I fitted a two sensor TM4 to my 2GM20 in the same manner as you did I and was very happy with it.

Engine Watchdog Temperature Monitors Comparison