Installing EGT Probe on Yanmar 4JH3

[Dockhead]

I run my 4JH3 HTE a lot at low power settings -- economical cruise I consider to be about 1800 RPM, and with my Brunton Autoprop in a dead calm or downwind in light wind (too light to set any sails), I can see 7 knots or even 7.5 knots with a clean hull, at that RPM.


Motorsailing sometimes I use even less RPM than that.


I have never really had any concern about this as the Yanmar manual specifically discusses "trolling" with this engine, using a special optional "trolling handle", at 1000 RPM. Yanmar require you to "blow out" the engine from time to time when operating it at low RPMs, and I do this.


Nonetheless, I got to thinking that it would be nice to not guess about whether a given operating regime is healthy or not, but rather actually monitor EGT. I already have a Maretron temperature module for my N2K network, which I use to monitor different things, and it has a pyrometer input on it. So I only need the probe, which is cheap as chips.


So maybe I'll throw one of these one. Anyone have any tips? I believe the exhaust manifold has a spot specifically for an EGT probe -- just drill it out, and tap it? How do you deal with the metal chips?

[Wotname]

Have a strong vacuum hose right beside the drill bit when drilling.
Coat the tap flutes with a thick grease when tapping.

[noelex 77]

As part of the commissioning process for our new boat, a Yanmar technician screwed in a probe with a handheld meter and made measurements at various revs.

I presume this was a EGT, but unfortunately he did not speak much English so I never had this verified.

I was a little busy at the helm making sure we did not hit anything in the channel. So I did not see exactly where the probe was placed, but the probe just screwed in place and was replaced I think with a blank plug when he was finished and happy.

The engine is Yanmar 4JH4-TE.

So there may be a spot already available.

[a64pilot]

I’ve done it on a truck motor and of course many airplanes.
Bu those don’t have water cooled exhaust manifolds.
Seeing as how you have a turbo, TIT or turbine inlet temperature or the PC TGT for turbine gas temperature is likely better and easier to accomplish.
On the truck it was drill a 1/8” hole and tap it for 1/8” NPT, measure depth, adjust the thermocouple for half that distance and install.
Aircraft it was drill a hole in each exhaust tube approx 2” from the head and install thermocouple, they were held in place by hose clamps.

My guess is that your dry exhaust is most accessible just before the turbo.

What I found was a performance Diesel usually didn’t exceed 1100 F very easily in stock trim and I limited mine to 1400 max. Aluminum melts at about 1200 F I think, but piston temp is nowhere near as high as exhaust temp.
Gas motors, aircraft anyway regularly ran about 1400 ish if memory serves. I ran my Lycoming 50f rich of peak, and a Continental 100f rich of peak.

A Diesel will idle at very low temps, less than 200f and a gas motor much higher. If I remember right I think my Duramax would idle about 150f.

An issue your going to have is what temp is high enough?
Duramax if an remember right ran down the road at 600 to 700 ?

All numbers in Fahrenheit.

[a64pilot]

Oh, and what was interesting to me, was if you pulled a hill loaded pretty heavy , the egt would of course climb, if it got high, I could push the accelerator down, which would force a downshift, engine would speed up and truck would begin to accelerate, but the EGT would drop.
Classic example of engine being lugged, increased RPM would increase airflow, which cooled the engine significantly, even though it was making more power

[SailRedemption]

The probe needs to be before the turbo for better and more accurate readings. There is a spot on the 4JH4-TE that I tapped into for the 1/8" npt probe fitting. Just unscrew the plug and drill/tap then rescrew the whole thing. See pictures

Also put a turbo boost fitting on the intake. Right before the heater where it bolts up.

I got my boost/EGT combo gauge from Seaboard Marine.

[Neziak]

Dockhead, did you do this in the end and where did you put the probe. I have the same engine - a 4JH3-HTBE. I note that there is a spot just before the wet exhaust elbow connection (pictured) that can be drilled out. Is this where you put it or did you put it before the turbocharger? Do you have numbers for max EGT for the engine? Thanks Nez

[malbert73]

Bumping this thread. Dockhead, did you install one? I am interested in same on my Beta since I am mildly overpropped (deliberately) and would be nice to know exactly where top end maxes out in different conditions

[tkeithlu]

If you want a plug and play, go to
All EGT Sensors Ultralite Aircraft

or other experimental aircraft supply house. Small airplanes use them to find the peak exhaust gas temperature, ergo the leanest mixture that fires properly.

[SailRedemption]

Originally Posted by malbert73

Bumping this thread. Dockhead, did you install one? I am interested in same on my Beta since I am mildly overpropped (deliberately) and would be nice to know exactly where top end maxes out in different conditions

I installed one on a Beta 60. Got it from Seaboard Marine. I had a bung welded on the exhaust riser. If you want a picture let me know.

[kenbo]

Since you have a Maretron gauge i'd contact them for the proper thermocouple. Most diesel thermocouples are k type. Also the length of the wire matters to if you want an accurate reading. I believe Yamnar's max temp for that engine is 1200 F and 750-800 F being the sweet spot.

[malbert73]

Originally Posted by SailRedemption

I installed one on a Beta 60. Got it from Seaboard Marine. I had a bung welded on the exhaust riser. If you want a picture let me know.

That would be great- mine is a beta 50 so similar I’m sure. Thx- no urgency

[bbayne]

Originally Posted by SailRedemption

I installed one on a Beta 60. Got it from Seaboard Marine. I had a bung welded on the exhaust riser. If you want a picture let me know.

I'm in the process of installing Beta43 and would like to add a pyro as well. Could you send pictures please. Thanks!

[malbert73]

I installed on a Beta 50 and replaced voltmeter on my display with the EGT gauge. I’ll try to find some pics. Had a professional install it since I don’t have ability to weld/tap stainless steel in the elbow

[bbayne]

Originally Posted by malbert73

I installed on a Beta 50 and replaced voltmeter on my display with the EGT gauge. I’ll try to find some pics. Had a professional install it since I don’t have ability to weld/tap stainless steel in the elbow

That would be great. Thank you! What temperature readings are you getting with your Beta 50?