Yanmar 4-JHE RPM's

[PuttingDoctor]

As a result of the other thread running re engine size I thought I'd pose the questions to those with Yanmar experience regarding the engine rpm's for motoring.

I had heard that these engines like to run hard but so far my experience seems to indicate that a lower power setting is not only more economical but also produces less heat.

I have a new 4" blower ready to install to help dissipate engine and engine house heat but wonder if taking it down a few notches might also be in order.

So, "What's your desired RPM with a Yanmar 4-JHE?"

Thanks for your replies.

[Tayana42]

I generally run between 2000 and 2500 rpm. 2200 is comfortable and economical for most conditions. As always, it depends on conditions. If I'm in a hurry for some reason, wanting to get into port before weather comes in for example I'll run at 2700 rpm. I have an 18" max prop and the boat is a 42 footer that is a 2,800# double ender with a 36' waterline and a 12.5' beam. She has a moderate fin keel and full skeg hung rudder.


S/V B'Shert

[a64pilot]

I run usually at 2000, sometime 2200. But I have an Auto prop that increases pitch as boat speed builds, so I'm within a half a kt of hull speed at 2200. 2500 puts me at hull speed and is a comfortable RPM, but the stern is squatted and I'm beginning to roll a wake at that speed. If your rolling a wake, the energy to make that wake comes from your fuel tank of course.
I know this may sound silly, but it just feels not stressed at 2,000 and is a relaxed sound.
You can run one at 2500 and up I'm sure for pretty much forever, 3400 is max continuous RPM

My boat came with a three" blower, but I don't see how a 4 would hurt anything at all

[japarker11]

PD,
We have put over 500 hours on our 4JH3-TE and a little less than 5000 nm in the last two years. It drives a 28,000# displacement boat through a 19" max-prop.

Our most efficient mode seems to be 2400 rpm, 7.0 knots at 1.33 gph. Move up to 2700 rpm, 7.3 knots and 2.1 gph. Above this heat EGT/turbo starts climbing and drive vibrations start to become painful. In a nasty seaway of wind against current we did run at 3100 rpm for two hours, too busy at the helm keeping the prop attached to monitor fuel burn.

Economy mode: we nursed a 65 gallon useful tankage with a 1400 rpm, 5.4 knot .35 gph run of 160 nm run across the Gulf of Alaska and Dixon Entrance.

We are losing our mix elbow about every 700 hours which is a painful experience.

I know the max HP is developed in the mid 3k range but with the hull speed limitation of displacement boats I don't think it would make sense to prop it to get there. So about 15 hp of the turbo is unusable. That is alright, I like the burn rates down low!

John

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[hpeer]

Elbow every 700 hours? Ouch!

We have just about 600 hours on our elbow, a custom SS rig.

Not looking forward to that. I hope we do better.

We have about 1300 hours on our 4jh4 ( what do those numbers mean anyway?)

The elbow was replaced at about 700 hours due to a bad installation. It seemed pretty good at that time.

I run anywhere from 1600 to 2200 rpm, tending to the lower settings. So far I'm not seeing any issues. I had a real bad vibration that took me forever to figure out. It was a muffler clamp hitting a member that resonated throughout the aft cabin, steel boat. The sound was coming from everywhere. Then one day, with the engine running easy and my head I the engine room, I could tell, just the right spot. Took 5 minutes to fix.

[a64pilot]

At least on the 4-JHE, there are two possible elbows, one looks like an elbow and keep an eye on that, it apparently fails early, the other looks like a box, mine is original at 28 years, but somewhat low hours, the box ones supposedly last a long time.
I believe some Hunters have this engine with a smaller exhaust than is considered normal too, maybe a 2"?


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[Vasco]

I run at 2350 most of the time. Sometimes when chasing bridges I'll go up to 2500 sometimes a tad over. Most I've ever run at is 2800. 4JH3E.

[GordMay]

For prolonged running, a pleasure boat engine a good operating speed is around 85% of maximum continuous rated RPM (see the engine data plate)
assuming the propeller size is correct and the engine can reach maximum rpm).
3/4JH4 series ±2400rpm
➥ Yanmar Marine Engine Help

[Hudson Force]

I run my naturally aspirated 4JH3E at near 2100rpm. This gives me 6.5 kts. with my 18x13 3-blade prop. I'm close to 7,000 hours with my only significant need beyond regular maintenance being a replacement of my oil cooler due to a vibration metal fatigue crack on the raw water pipe. I still use my original mixing elbow.

I do run a 3" exhaust fan in my engine room when running, but this is not for concern with my engine temperature, but to reduce the heat in the area where my refrig/freezer is exchanging heat.

[Dockhead]

I run my 4JH3-HTE (same engine, but turbo and intercooler, 100hp) at anything from 1800 RPM to 3000 RPM depending on the need for power. Mostly about 2000.

Exhaust elbow was replaced at 2000 hours because of perforations. It never carboned up and I never cleaned it even once.

I follow the Yanmar manual and run it up to near redline for a few minutes every couple of hours. Also when anchoring I always run the engine at redline while doing final backing down on the anchor.

I don't think that there is any problem running these engines at whatever low RPM you might need, so long as you have a load on (like A64, I have an Autoprop which helps with this), and as long as you run it up once in a while as instructed.

These engines could be had with trolling levers for the specific purpose of running at below 1000 RPM, so I don't think Yanmar has any problem with it.


Concerning the blower: The more the better.

[PuttingDoctor]

Thanks for all the input. I think my original take was a little wrong. The issues I saw with heat have resulted in replacement of the exhaust manifold / heat exchanger which showed electrolysis corrosion. I am installing a 4" blower fan more for keeping engine heat from the cabin on shutdown.

New procedures will have a constant rpm more in the 2-2300 range with regular exercise in the higher rpm's on long motoring times and prior to shutdown.


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[Dockhead]

Originally Posted by GordMay

For prolonged running, a pleasure boat engine a good operating speed is around 85% of maximum continuous rated RPM (see the engine data plate)
assuming the propeller size is correct and the engine can reach maximum rpm).
3/4JH4 series ±2400rpm
➥ Yanmar Marine Engine Help

That's a typo -- the linked site says 2900RPM.

But 85% of my 4JH3HTE's max continuous would be 3230.

While the 4JH engines are smooth as silk compared to many other marine diesel engines of this size (I was amazed when I found out that they have no balance shafts), they don't sound nearly as happy at those speeds, as they do around 2000 to 2300 RPM, which for my engine is 52% to 60% of max continuous (which is 3800).

I would not get hung up on that 85%. An engine that sounds happy, IS happy. Just run it up to near redline under load from time to time, as Yanmar instructs.

[Dockhead]

Originally Posted by PuttingDoctor

Thanks for all the input. I think my original take was a little wrong. The issues I saw with heat have resulted in replacement of the exhaust manifold / heat exchanger which showed electrolysis corrosion. I am installing a 4" blower fan more for keeping engine heat from the cabin on shutdown.

New procedures will have a constant rpm more in the 2-2300 range with regular exercise in the higher rpm's on long motoring times and prior to shutdown.


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Good plan

[Phoenician]

Not much to add to what's been posted above. FWIW, here is my measured fuel consumption at various rpms of my Yanmar 4JH3-HTE, all in very flat sea conditions over several hours of navigation:

1900 : 2.8 L/H
2000: 3.1 L/H
2200: 3.7 L/H
2500: 5.7 L/H


And I just had to change the mechanical seal on the seawater pump after 1900 hours. Exhaust elbow still OK as far as I can see

[Dockhead]

Originally Posted by Phoenician

Not much to add to what's been posted above. FWIW, here is my measured fuel consumption at various rpms of my Yanmar 4JH3-HTE, all in very flat sea conditions over several hours of navigation:

1900 : 2.8 L/H
2000: 3.1 L/H
2200: 3.7 L/H
2500: 5.7 L/H


And I just had to change the mechanical seal on the seawater pump after 1900 hours. Exhaust elbow still OK as far as I can see

Very useful data. What prop do you have, and what speeds do those revs correspond to, in flat water and no wind?