Place to put temperature gauge on Yanmar 3HMF

[joeniver]

I would like to put a dial gauge in addition to the overheat alarm on my Yanmar.
I would like some suggestions on where it could be installed on my engine.

I was thinking to put a fitting in the water pump for the water coming out of the engine. How would I do that without slowing down the flow?

Any suggestions welcome
Joe

[Wotname]

You could the same spot as the existing overheat switch. Remove the switch and replace it with a combination sender and switch.

[IslandInfedel]

If you already have a alarm for water temp, why not add a oil or head temp readout?

[Wotname]

Originally Posted by Wotname

You could the same spot as the existing overheat switch. Remove the switch and replace it with a combination sender and switch.

Opps - typo! Should read "You could use the same spot etc"

[joeniver]

Thank you for your reply.
You say to use a sender and a switch. What do you mean by the switch? Would that me a switch that changes from meter reading to a alarm reading.

I don't understand what you mean. Also with there be an issue of the threads between a US device and the existing Japanese threads?

Thank you for your help.
joe

[malbert73]

You could also plumb an aftermarket temp gauge into the water heater lines using hose barbs and clamps if your boat is equipped. Right after engine exit- I did this on my prior boat 3YM30 and it worked perfectl

[Wotname]

Originally Posted by joeniver

Thank you for your reply.
You say to use a sender and a switch. What do you mean by the switch? Would that me a switch that changes from meter reading to a alarm reading.

I don't understand what you mean. Also with there be an issue of the threads between a US device and the existing Japanese threads?

Thank you for your help.
joe

Let's see if the following makes it clearer.

The existing Yanmar alarm uses a over temperature switch. It is a ON/OFF device. It is OFF at normal temperatures and changes to ON when the temperature rises above the threshold. This causes the lamp to illuminate and if fitted, the buzzer to sound.

A temperature gauge requires a variable resistance device that changes resistance as the temperature changes. It is commonly called a sender or sometimes a sensor.

They can be packaged separately or in a combined unit. The combined unit has a one terminal for the alarm (switch) function and a seperate terminal for the gauge (sender) function. Inside the unit the switch function is isolated from the sender function.

The 3HMF engine usually uses BSP (British / European) thread while the USA standard thread is NPT. IIRC, the 3HMF is a 1/8" BSP and if you are using the USA NPT threaded item, the following BSP/NPT adapter will work.
https://www.aliexpress.com/item/4000...archweb201603_

BTW, you need to make sure the sender is electrically compatible with the gauge as there are several different standards.

[fritzdfk]

On my 3HM I installed a CruzPro temp gauge. It has an alarm function and digital temp display. You just need to replace your existing temp sender switch with a temp sender. The CruzPro is compatible with almost all temp senders. You would need to get a temp sender that has BSPT thread.
CruzPro T60 Digital Water Temperature Gauge and Alarm

[wingssail]

Originally Posted by Wotname

...The 3HMF engine usually uses BSP (British / European) thread while the USA standard thread is NPT. IIRC, the 3HMF is a 1/8" BSP and if you are using the USA NPT threaded item, the following BSP/NPT adapter will work.
https://www.aliexpress.com/item/4000...archweb201603_...

Funny thing about these threads. I ran into the same problem trying to install a mechanical oil pressure gauge on my Yanmar. The fitting for the gauge was NPT 1/8 27 and the Yanmar apparently uses a BSP 1/8 28.

I bought two of the adaptors listed above.

Didn't work. They only threaded in about 2 threads then stopped. Same as the actual mechanical gauge fitting. I tried several combinations with various fittings. In all cases the male BSP go in fine to the female side of the adaptor, but not the other way around.

Maybe the company sent me the wrong adaptors, they are not marked.

But I also bought a BSP 1/8 28 die and I was able to rethread the adaptor and that worked, however there is one thread in the middle which is broken. Not sure what actually happened.

So, don't be surprised if you run into a problem with the BSP to NPT adaptor.

[a64pilot]

It’s tough to find a dual use switch / sender, then add in the right resistance sender and it gets even harder.
On my Yanmar right beside the temp switch there was an unused hole with a plug in it, remove the plug and screw in the temp sender, on mine you can see that it took a bushing to change the size, the switch can be seen in the photo right behind the sender. Switch has a green top, sender a white wire. On mine NPT worked fine, but it’s easy to tap BSP to NPT, the threads are so close, it’s more of a thread straightening than tapping.

[Wotname]

Originally Posted by wingssail

Funny thing about these threads. I ran into the same problem trying to install a mechanical oil pressure gauge on my Yanmar. The fitting for the gauge was NPT 1/8 27 and the Yanmar apparently uses a BSP 1/8 28.

I bought two of the adaptors listed above.

Didn't work. They only threaded in about 2 threads then stopped. Same as the actual mechanical gauge fitting. I tried several combinations with various fittings. In all cases the male BSP go in fine to the female side of the adaptor, but not the other way around.

Maybe the company sent me the wrong adaptors, they are not marked.

But I also bought a BSP 1/8 28 die and I was able to rethread the adaptor and that worked, however there is one thread in the middle which is broken. Not sure what actually happened.

So, don't be surprised if you run into a problem with the BSP to NPT adaptor.

Thanks for the warning.

[Wotname]

Originally Posted by a64pilot

It’s tough to find a dual use switch / sender, then add in the right resistance sender and it gets even harder.
.....

This true and I always suggest one buys the sender and and the gauge together unless one is fully aware of the various resistance requirements.

As for a dual switch / sender, VDO make several (with and without isolated grounds) although AFAIK, VDO uses a propriety resistance scale and thus one needs to use a VDO gauge as well as the VDO sender.

Perhaps VDO makes senders for all ranges, they certainly have enough part numbers .

[Nani Kai]

Originally Posted by a64pilot

It’s tough to find a dual use switch / sender, then add in the right resistance sender and it gets even harder.
On my Yanmar right beside the temp switch there was an unused hole with a plug in it, remove the plug and screw in the temp sender, on mine you can see that it took a bushing to change the size, the switch can be seen in the photo right behind the sender. Switch has a green top, sender a white wire. On mine NPT worked fine, but it’s easy to tap BSP to NPT, the threads are so close, it’s more of a thread straightening than tapping.

I have been trying to achieve this on both of my Yanmar 3YM30's. I have Stewart Warner gauges I want to install at the helm and Yanmar sensor/senders. The problem is I can't figure out where to install the sensors. I want to maintain both the current Overheat Alarm switch/warning light in addition to adding the temp sensor and gauges. So far I haven't located that extra plugged hole. What model Yanmar engine do you have?

[Wotname]

Originally Posted by Nani Kai

I have been trying to achieve this on both of my Yanmar 3YM30's. I have Stewart Warner gauges I want to install at the helm and Yanmar sensor/senders. The problem is I can't figure out where to install the sensors. I want to maintain both the current Overheat Alarm switch/warning light in addition to adding the temp sensor and gauges. So far I haven't located that extra plugged hole. What model Yanmar engine do you have?

Here is a screenshot of the 3YM30 fresh water pump from the service manual. Maybe the one of the two red circled plugs could be used along with a suitable adapter.

[malbert73]

Or do what I did with my 3ym30 on my old boat- get a brass plumbing T fitting and plumb it with hose barbs into your hot water heater heat exchanger lines just after engine outlet- and the sender goes in the T fitting as well using an adapter. Worked perfectly.