Yanmar temperature sensor

[joeniver]

I have a meter that tells the exact water temperature-fresh water-but I don’t know where to install it. My engine is a 3HMF. The sensor is at least 5/8” if not more.

Any help would be appreciated.
Joe
New to this forum

[a64pilot]

Look around, there is usually a pipe plug that you remove. If you find such a plug and I bet you will, then find a sensor that fits the hole, mine I believe was 1/8 npt.

[joeniver]

Thanks a64pilot. Will send u a pic.

So you get to sail for most of the year?

Most get hauled out here in Long Island.
Joe

[a64pilot]

This is my 4-JHE, the sender with the white wire I added for a gauge, the original factory switch for the alarm you can see immediately below it. After looking you can see it’s considerable larger than 1/8” NPT, maybe 3/8”?

[joeniver]

My engine is 3HM. Around 1984? The sensor is 5/8".
Will I need to get a reducing or expanding nipple to make it fit?

Thank you for you help!
joe

[pcmm]

Originally Posted by joeniver

My engine is 3HM. Around 1984? The sensor is 5/8".
Will I need to get a reducing or expanding nipple to make it fit?

Thank you for you help!
joe

What kind of temp sensor is that? Very different from what I've seen in the past. Usually the sensor looks like A64pilot's just a small device that you screw in and connect a single electrical lead to.

[joeniver]

It is a mechanical sensor. Does not need electricity for it to function. If it does not work, I will get one like a64pilot has.
Thanks

[Wotname]

Originally Posted by joeniver

I have a meter that tells the exact water temperature-fresh water-but I don’t know where to install it. My engine is a 3HMF. The sensor is at least 5/8” if not more.

Any help would be appreciated.
Joe
New to this forum

As a64pilot posted, there are a couple of plugs in the cooling system that can be removed for the fitting of another temperature sensor. You will see in the attached parts breakdown, there are three near the existing coolant pump and thermostat (items 9,12 and 13) and another in the coolant tank (item 21).

Item 12 is 1/4" BSP and the others are 3/8" BSP (British Standard Pipe). Note this isn't the actual diameter of the thread.

I don't know the type of thread your sender has although all the mechanical senders I have seen are BSP. Presumably you are located in North America and therefore your sender may be different. Maybe the supplier knows?

[joeniver]

Thanks WotName:

Great diagrams. Do you know where I can get that service manual? I only have engine installation --brief-- and operation and light trouble shooting.

Will take a deeper look at the engine today.

Will I have to order all pipe fittings since they are BSP? Is not American plumbing the same as British?

Also for starting and running, do I have to keep the idiot light temp sensor connected? I would like to just put a reducing nipple where the sensor is now.

Thanks for your help.

Joe

[pcmm]

Originally Posted by Wotname

As a64pilot posted, there are a couple of plugs in the cooling system that can be removed for the fitting of another temperature sensor. You will see in the attached parts breakdown, there are three near the existing coolant pump and thermostat (items 9,12 and 13) and another in the coolant tank (item 21).

Item 12 is 1/4" BSP and the others are 3/8" BSP (British Standard Pipe). Note this isn't the actual diameter of the thread.

I don't know the type of thread your sender has although all the mechanical senders I have seen are BSP. Presumably you are located in North America and therefore your sender may be different. Maybe the supplier knows?

Its true that Yanmar uses BSP thread, which is really a pain as BSP are impossible to find. Luckily NPT and BSP are close enough to be compatible. The ones near the thermostat are for an optional hot water tank circuit but as they are on the closed side of the thermostat, either would be great options for a temp sensor.

[Wotname]

Originally Posted by pcmm

Its true that Yanmar uses BSP thread, which is really a pain as BSP are impossible to find. Luckily NPT and BSP are close enough to be compatible. The ones near the thermostat are for an optional hot water tank circuit but as they are on the closed side of the thermostat, either would be great options for a temp sensor.

You are boating in the wrong part of the world; BSP is available everywhere in the right parts of the world .

As for the BSP / NPT compatibility, I have found that NPT male fittings can be fitted into BSP female threads if you use a liberal amount of pipe sealant. However trying to fit BSP male fittings into a female NPT thread always ends in tears.

[Wotname]

Originally Posted by joeniver

Thanks WotName:

Great diagrams. Do you know where I can get that service manual? I only have engine installation --brief-- and operation and light trouble shooting.

Will take a deeper look at the engine today.

Will I have to order all pipe fittings since they are BSP? Is not American plumbing the same as British?

Also for starting and running, do I have to keep the idiot light temp sensor connected? I would like to just put a reducing nipple where the sensor is now.

Thanks for your help.

Joe

A HM service manual can be downloaded from the library section of CF Cruisers & Sailing Forums - Library - Manuals

If you PM me with an email address, I can send you an illustrated parts manual for the 3HM35. The fie size is about 6MB.

You don't have to keep the existing over temperature switch and idiot light (and buzzer) but I would recommend keeping it. One doesn't always keep watching the gauge (or idiot light) but the audile alarm associated with the idiot light is a very good thing IMO.

The American plumbing system is rather odd and not all standard - OK, that was a joke!

[a64pilot]

Originally Posted by Wotname

You are boating in the wrong part of the world; BSP is available everywhere in the right parts of the world .



As for the BSP / NPT compatibility, I have found that NPT male fittings can be fitted into BSP female threads if you use a liberal amount of pipe sealant. However trying to fit BSP male fittings into a female NPT thread always ends in tears.

Not for the 1/8”, maybe it was 1/4”? however they are close enough so that you can take a tap and cover it with grease to hold any cuttings and tap out an oil galley, then thread in the oil sending unit.
Oil senders are usually small. Temp are usually larger.
On the 4JHE anyway there are plenty of unused plugs so that you can install a temp gauge and oil pressure sender and not touch your factory switches or wiring.

That is how I installed my oil PSI gauge, on the advice of a Yanmar dealer after trying unsuccessfully to find an adapter.

[joeniver]

Me email address is joeniver@hotmail.com thanks