3JH3E Thermostat Details

[Nineteen]

Hi All

I am not near my boat to measure at the moment but would like to get a spare thermostat. The engine is a Yanmar 3JH3E.

I believe the part number is 129470-49801, it is a bypass type rated at 76.5°C and I think offset but I would prefer not to pay the Yanmar price......

So has anyone out there got one that they can measure for me?

If so I need the following info:

1) The diameter of the main body disk.
2) The diameter of the bypass valve disk.
3) The overall height between the two disks when cold/closed.

There should be an aftermarket alternative available I hope.

I have attached a photo of a bypass thermostat to hopefully help with a reference.

Thanks in advance.

Cheers
Tom

[boden36]

I have the same motor and am intrigued as to why you would need a spare thermostat.

Regards,
Richard

[Bruce Beard]

I always keep a spare thermostat aboard! That way I probably will not need one....
I have a 3JH4e and the thermostat is over $75.00 these days. Yanmar parts are getting pretty expensive.
I replace my thermostat every 1000 hours on our diesel.
Just to be sure! Of course I spent my working life maintaining European autos and I have seen most parts fail at one point or another...

[Bruce Beard]

Just for the record, I would just buy the correct part if I were you...

[Nineteen]

Hi Richard

I use a preventative maintenance philosophy.

Earlier this year I gave the heat exchanger and the rest of the cooling system a proper birthday when it was due for its scheduled flush/coolant change. The engine was 14 yrs /1965 hrs old at the time. Appart from running green coolant I did'nt really find any issues as the PO had serviced the vessel and maintained a log. I did however have the heat exchanger pickled and replaced all hoses.

Unfortunately I forgot to grab the thermostat details but it tested ok at the time.

As the unit is still the original, and I dont want to get stuck I just would like to have a spare on board.

Cheers
Tom

[Nineteen]

Originally Posted by Bruce Beard

Just for the record, I would just buy the correct part if I were you...

Hi Bruce

It may come to that - and I have bought genuine where necissary. I am just exploring options. Yanmar may have had a specific thermostat but I would be surprised.

I have my diesel ticket and fix aeroplanes for a living. I am just trying to look after the boat in a simmilar fashion ;-)

Cheers
Tom

[boden36]

Tom, I can see where you are coming from, and it probably is a good idea as it does not take up a lot of space. The reason I commented was that in a pinch, the engine can get you home OK with the thermostat removed. (Which does not help you much with your original question I guess!)
Regards,
Richard.

[Nineteen]

Originally Posted by boden36

Tom, I can see where you are coming from, and it probably is a good idea as it does not take up a lot of space. The reason I commented was that in a pinch, the engine can get you home OK with the thermostat removed. (Which does not help you much with your original question I guess!)
Regards,
Richard.

Hi Richard

All good - you are absolutely right.

Anyway, I've put it out there so we shall see if anyone can supply the numbers. Worst case scenario is next time I'm on board (hopefully in a week or so), I will pull it out. I was just hoping to save the half hour!

Cheers

[Brickwede]

Hello nineteen,
I'm also seaching for a original replacement of the 129470-49801 Thermostat.
But at time no part for a replacement found.
Do have your measures done? I have an old faulty Thermostat available. When I have found it in my spare part box, I'll send you the dimension.

[Nineteen]

Originally Posted by Brickwede

Hello nineteen,
I'm also seaching for a original replacement of the 129470-49801 Thermostat.
But at time no part for a replacement found.
Do have your measures done? I have an old faulty Thermostat available. When I have found it in my spare part box, I'll send you the dimension.

Hi Brickwede

Sorry for the late reply - on course at the moment.

I did pull my thermostat and was able to get the size but could not get anywhere close to the 76.5°C rating so I bought a genuine.....

I guess Yanmar get them made at that temp by NTC and thats it. The auto ones open at a higher setting which would probably lead to salt precipitation in the heat exchanger.

It cost me $150AUD but at least I have my spare. ;-)

Cheers
Tom

[GordMay]

Greetings and welcome aboard the CF, Brickwede.