Adding a temperature guage

[Macblaze]

I admit it, I know nothing about diesels and haven't worked on a motor since the 80s when I could still tell what I was looking at. But my boat came with an idiot light and alarm that only works intermediately when I turn the engine off and on and I keep thinking I should add a temperature gauge.

But I have no idea what that entails. Are there sensors already installed and I just need to add a gauge? Or is it more in-depth than that? It's a 2003 Hunter with a Yanmar 3JH3E. Not looking for step by step instruction but rather just an idea of how big a project it would be.

[pcmm]

The "intermitent" light is supposed to come on when you first start the engine. its normal. but to add a temp sensor to a Yanmar you have 2 choices. Get a yanmar branded sensor and gauge ( get used to reading in "bar") or get an adapter for the port and use regular North American gauges. You need an adapter because Yanmar engines are metric, but use BSP threads on their fittings which "sort of" work with NPT. The taper isn't quite the same an the TPI is different. It works OK on the water heater if you add the circuit after market but I wouldn't do it for the oil pressure. Thankfully the adapters can be found online for only a few $, then you just need to find a gauge and sender of your choice.

[Macblaze]

Originally Posted by pcmm

The "intermitent" light is supposed to come on when you first start the engine. its normal. but to add a temp sensor to a Yanmar you have 2 choices. Get a yanmar branded sensor and gauge ( get used to reading in "bar") or get an adapter for the port and use regular North American gauges. You need an adapter because Yanmar engines are metric, but use BSP threads on their fittings which "sort of" work with NPT. The taper isn't quite the same an the TPI is different. It works OK on the water heater if you add the circuit after market but I wouldn't do it for the oil pressure. Thankfully the adapters can be found online for only a few $, then you just need to find a gauge and sender of your choice.

The intermittent part is the light only comes on half the time :-)

So you are saying there is a "port" somewhere in the cooling system? And what needs to be done is to add a sensor (and likely an adapter) and run wires back to the binnacle. And I totally forgot about the oil pressure...I assume it is another "port"?

[hellosailor]

Mac-
You really need an engine manual to DIY on this. An idiot light normally will be connected to a *switch* that turns it on and off. A temperature gauge will be connected to a variable resistor. Either one looks pretty much like an extra spark plug that has been screwed into the engine someplace, and depending on the particular engine and maker, it might be as simple as unscrewing the one that's in the engine block, and replacing it with the other. (And instrument, of course.)
Or there might be a different hole, with a plug in it, that's removed.
There are also "universal" temperature gauge sensor kits. They replace a short radiator hose and the sensor is tapped into them.
Bear in mind that "the" temperature is going to vary depending on the cooling system and just how far downstream the sensor is, so if you can find out what the factory intended and follow it, that's probably the best way to go.

[pcmm]

Originally Posted by Macblaze

The intermittent part is the light only comes on half the time :-)

So you are saying there is a "port" somewhere in the cooling system? And what needs to be done is to add a sensor (and likely an adapter) and run wires back to the binnacle. And I totally forgot about the oil pressure...I assume it is another "port"?

Have a look here:

http://sagaforumet.com/yanmar-manual...kapittel_9.pdf

look at section 9-37 the water temperature sending unit is on the side of the thermostate housing.

[Wotname]

Originally Posted by Macblaze

I admit it, I know nothing about diesels and haven't worked on a motor since the 80s when I could still tell what I was looking at. But my boat came with an idiot light and alarm that only works intermediately when I turn the engine off and on and I keep thinking I should add a temperature gauge.

But I have no idea what that entails. Are there sensors already installed and I just need to add a gauge? Or is it more in-depth than that? It's a 2003 Hunter with a Yanmar 3JH3E. Not looking for step by step instruction but rather just an idea of how big a project it would be.

Advice upthread is good but let me add more.

There are two routes you can take, an easy one and a slightly harder one.

These days, adding temperature sensors can be easy if you use something like a "Engine Watchdog" or "Engine Guard". Here are two examples but I'm sure there are many more. ENGINE WATCHDOG Audible Engine Overheating Alarm, Gauge & Sensor & https://engineguard.com.au

In essence you bolt a external sensor onto a convenient part of the head and provide a 12v positive and negative lead to the display. As well as providing a digital readout of the temperature of the sensor, most have alarm points that are user set. For instance, if your normal operating temperature is say, 145F, then you can set the alarm trip point to say 150F or 155F or whatever you feel comfortable with. Also lot of these monitors have two sensors. I fitted a Engine Watchdog with a sensor on the water jacket of the head and the other sensor on the mixing elbow of the exhaust. These monitors will work on any engine and are easy to fit!

The slightly harder method is to follow the traditional route with a sensor placed IN the water jacket somewhere and run a wire to a traditional gauge. The gauge will still need a 12V pos and neg leads.

I'm not familiar with your Yanmar but the other small Yanmar marine diesels I am familiar with do not have any spare water jacket ports that you can use. However the Yanmar over temperature alarm switch can be removed and a T piece fitted and the temperature sensor placed into the T piece along with the original over temp. switch.

The picture shows the over temp. switch on a 2GM20 but it similar to most other small Yanmar marine diesels. I have also highlighted a spare threaded hole which I used to attach an external sensor. Unfortunately I don't have a picture of the completed project after fitting the external sensor.

As other have posted, Yanmar uses BSP threads rather than NPT threads (the more usual North American thread). Although not best practice, you can fit a male NPT into a female BSP but not vice versa. Thread sealant is advised especially when mixing threads!

[Macblaze]

Thanks all!

I think I ma getting the picture. I am a thousand miles away from the boat (and the manual) so I need something to fuss about :-)

Anyway this gives me plenty to start with and I will research my particular engine and see if it's a project for next spring. Thanks for getting me up to a point where all the other bits will make a bit of sense...and the warning about the threads!

[Cheechako]

Yes, you just need a "sender" and gauge. Then find a place on the engine cooling jacket to install it. The idiot light sender is there somewhere, use that port. You can get a "dual" sender that does the light and the gauge.

[Suijin]

While your at it add an audible overheat alarm. No one stares at their temperature gauge the whole time and a bad overheat can ruin more than just your day.

[mikecambrai]

I have added 3 thermal switches to my engines. The first measures Jabsco temperature, the second water jacket temperature and the third the temperature of the exhaust manifold where the water is injected. On the Jabsco I attached the switch with epoxy, on the water jacket to a convenient metal pipe through which water flows and the on exhaust pipe with wire.
So I now have an alarm which tells me when the exhaust manifold goes above 60 C (it is cooled by the engine water), the Jabsco goes above 50C (you only have a couple of minutes with a Jabsco) and the water jacket at 80C.
You can get sensors at various temperature settings depending on what you are happy with.

[Library70]

I have a Yanmar 4JH3 that I added a temp gauge and sender to. Where the water heater hose was tapped into on the top of the engine I removed the elbow and added a "T", put the temp sensor in the T. The engine was already prewired,the wires were bundeled and wrapped near where I installed the sensor. I used an aftermarket gauge and sender that came packaged together.
Definitely worth the effort, it's great peace of mind.

[jmschmidt]

I did it on both coolant temp and oil pressure on my Mitsubishi/Vetus engine. BSP (British Standard Pipe) taps and dies are readily available. Got BSP dies and re-ran the threads on NPT copper nipples and screwed them right into the block, no problems for twenty years.

Don't know why the Japanese use BSP and not metric for this. Could be when the Brits tore up all the narrow-gauge railways in the late-1800s and shipped them to Japan, the Japanese just adopted the BSP standard for pipe thread. There is only about one pitch per inch difference between BSP and NPT, BSP being the finer, I recall.

[Jeanneau 45.2]

PCMM: Thank you for posting the link from the Saga forum. I have several OEM manuals, none of which are as clear or explicit as this one. Very clear information as to where to tap for engine oil pressure and water temperature sending units to supplement the idiot lights.

[jmschmidt]

You shouldn't have to tap the block at all. You can probably add coolant temp and oil pressure gauges to your existing setup as follows:

1. Simply re-running the treads on appropriate sized nipples for your existing BSP holes with a BSP die.

2. Install tees on the ends of the nipples before installing in the block.

3. Install the idiot light and warning buzzer senders on one side of the tees.

4. Install the senders for cheap auto shop quality oil and water temp gauge sets on the other end of the tees.

5. Run the wires and install the gauges where ever you want.

Has worked for me for 25 years.

[a64pilot]

Good luck finding a BSP to NPT adapter.
I chased my threads with a 1/8” NPT tap with grease on the tap, your not really cutting threads, more like straightening them as BSP and NPT are very close.
That was for oil, the temp transducer threaded right in.