Yanmar 4JH3TE, 75 hp - turbo

[Matt Y]

We are pretty close to making an offer on a boat that is quite well put together and maintained, in almost all areas but the engine, which could have had a bit better tending and perhaps pattern of use... I guess it is always something....

Anyway, I am no engine specialist, for sure, but have asked the seller a bunch of questions to get a sense of how the engine has been used and maintained and am reaching out for advice and perspective on some concerns we have.

The engine is a 2006 Yanmar 4JH3TE, 75 hp - turbo coupled with a KANZAKI KBW21 trans. There are 3,000 original hours, over 8-years of continuous live aboard use covering 40,000 miles with 4 ocean crossings. The boat is equipped with a genset and 260 watts solar, so engine not normally use for charging.

The sellers report they run at 1,800 rpm when motoring, and have NEVER run it in the 2,800 – 3,800 RPM range. This particular engine is OEM rated for 3,800 rpm WOT, so in effect, it has motored 3,000 hours at less than 50% rated rpm and never been brought above 70% rpm rating....

We are very concerned about the prospects of carbon buildup and much worse about the prospect of bore glazing/ polishing which if the case would likely require a strip down to have the bores honed and new rings fitted.

We are hoping for shared perspective on what diagnostics we might want performed as part of an engine survey in this instance, and even more relevant, how likely the engine is to have significant problems from such a usage pattern. Also, how reliable would the recommended tests be for definitively determining if there are issues?

With much appreciation,

Matt

[delmarrey]

That's what an engine survey is for.

When you rev it up in neutral, which you're supposed to do before shutdown, does it blow black smoke/carbon?

[CarlF]

While this certainly is not ideal, it was under load so probably reached operating temperature at 1800 rpm quite quickly. Most of the things you mentioned come from engines operating at a low temperature.

The far more common problem of being run an hour a day at 1200 rpm for battery charging would have been far worse.

I'd take it out and confirm that at 1800rpm the temperature is at 180-190F.

And be realistic. An engine with 3000 hours is not new. Things are going to break and wear out. No survey can protect your completely. This is presumably reflected in the price of the boat (or will be after negotiations)

[barnaclejim]

Yanmar makes a great engine. We have a 98 140 horse LDTE and its rated at a higher rpm for efficient use but we almost always run at 12 to 1500 rpms and all is good after 3800 hours, no smoke or oil burning very dependable and pretty straightforward and parts available most anywhere. Best of luck

[sailorboy1]

an engine with 3000 hours on means that it runs just fine

[djmarchand]

Tony Athens, the diesel engine guru and moderator of boatdiesel, has said that he has never seen a marine engine harmed by running too slow. That may not be entirely true as one of the previous posters noted that running a sailboat engine half the night at 1,200 rpm to recharge batteries is not good for them. So is running a genset all night at essentially no load for days on end.

But 1,500 rpm pushing the boat should be fine. Take it out and run it hard for 15 minutes to blow out any accumulated soot. If the engine revs to rated rpm without significant black soot it is fine. At worst you might have to replace the exhaust elbow which is a 1,000 hour maintenance item in any case.

David

[HappyMdRSailor]

Matt...

First of all WELCOME to CF!
(where are my friend's manners today? Probably frazzled because one of our friends is disabled and becalmed off Horta, and everybody else has their hackles up over some young sailors... I digress...)

Anyway... I am not a "certified" diesel expert, but have more experience than most... tearing apart, rebuilding, repairing, and sometimes band-aiding motors...

My opinion??? If I was to inherit an engine with that number of hours on it... I would count myself lucky if it were something just as you have... A large displacement "un-overworked" example... Like CarlF mentioned.. as long as she gets up to operating temp quickly at 1800 (she will) I don't think you have anything to worry about...

Obvious and already mentioned... She's not new, so things are likely to go here and there... IP, injectors, turbo seals, exhaust/exchangers... on and on... But this is a boat, and what happens...

If you want some piece of mind... Have an engine survey done... You're looking for wet and dry compression values... Compare these directly to factory specs... Pull the valve cover, and look at the condition of the valve gear, general observation of cleanliness inside the engine... this will give you a good indication of how it was really maintained... Oil analysis is extremely overrated in my opinion... If the person performing the tests and inspection were pleased... You probably could stretch putting 3000hrs/8yrs/40k/4 crossings on her yourself!

We all love to help... Keep asking questions... We'll keep answering!

[Dockhead]

Originally Posted by sailorboy1

an engine with 3000 hours on means that it runs just fine

LOL. Indeed.

I have a 4JH3HTE, which is the same engine but with an intercooler and so 100 horsepower. The manual specifically describes how to use it for trolling at low RPM (like 1000).

I don't think there's anything in the world wrong with running it at 1800 RPM under load -- I do that with mine all the time.

Now I do run it up to 3600 RPM on a fairly regular basis.

If it is not burning oil or smoking at 3000 hours, I think you're probably good for another 3000 hours, but a thorough survey is a good idea in any case.

Yanmars often smoke, by the way. Mine emits billows of blue-grayish smoke under some conditions, and has done so since I bought the boat five years ago at 830 hours. But does not burn oil and starts perfectly. 1600 hours on it now.

[CarlF]

I also have never actually heard of a Yanmar having a carbon problem. I'm sure it happens but not enough to generate many stories for the marina watering hole. The exhaust elbow is a different issue but mine is over 1500 hours with no significant narrowing or corrosion.

The problems you do hear about with Yanmars is engine damage from overheating (running too hard or cooling failure) and damage from low oil or missed oil changes.

It doesn't sound like either is your problem.

[HappyMdRSailor]

Originally Posted by CarlF

I also have never actually heard of a Yanmar having a carbon problem. I'm sure it happens but not enough to generate many stories for the marina watering hole. The exhaust elbow is a different issue but mine is over 1500 hours with no significant narrowing or corrosion.

The problems you do hear about with Yanmars is engine damage from overheating (running too hard or cooling failure) and damage from low oil or missed oil changes.

It doesn't sound like either is your problem.

There are lovers and haters of every engine.... But this I agree with... overheating or bad maintenance.... You WILL have a problem...

[Matt Y]

Thanks for the welcome and suggestions/ perspectives. Sounds like the consensus here is we likely have little to worry about from the sellers relatively low 1800 rpm motoring history-- although I would love to hear from any decenter(s) who have knowledge or experience to the contrary...

I think confirming that the engine at 1800 rpm under load quickly achieves 180-190F operating temperature is a great suggestion!

Is there any concern running to 3800 rpm WOT on a 3,000 hour engine that has NEVER been run close to 2,800 rpm? Also, what approach if the seller refuses to do so, other than the obvious prospect of a serious price reduction?

The surveyor we work with observes WOT while monitoring temperature, rpm, boat speed and visuals on exhaust, but for peace of mind, we will likely pull in a marine diesel mechanic for a more comprehensive engine survey to include dry & wet compression tests. Any recommendations for a trained, experienced and conscientious marine diesel mechanic in the Port Canaveral, FL area?

Since the fluids are due for a change (with a known number of hours and duration since last changed), we will also have them pulled for analysis at Blackstone Labs.

With appreciation,

Matt

[Cheechako]

I wouldnt worry about glazing with that use, as long as there's a decent load on it , it's not going to glaze..in fact, it may be more excessively loaded at that rpm if overpropped. But carbon is possible... especially in the exhaust elbow. 1800 seems pretty low even for me who might rather be at 2300!
If you can get a sense for how much (or any) oil it's burning, removing the head and rebuilding/decarboning isnt the end of the world. (if it even is a problem.... which isnt a given)
He must be way overpropped if he's happy running at 1800 rpm.... so you may not be able to run the engine at 3000+ in testing.
It's just hard to say really.
The turbo may scare me more. Another angle or two: 1)He's lying about the rpm and the engine exhibits problems at higher rpm. 2) or the engine is really like a low hours engine because at 1800 rpm it's only had what... maybe 60% or the revolutions of a 3000hours 3200 rpm engine!

[HappyMdRSailor]

Originally Posted by Matt Y

Thanks for the welcome and suggestions/ perspectives. Sounds like the consensus here is we likely have little to worry about from the sellers relatively low 1800 rpm motoring history-- although I would love to hear from any decenter(s) who have knowledge or experience to the contrary...

I think confirming that the engine at 1800 rpm under load quickly achieves 180-190F operating temperature is a great suggestion!

Is there any concern running to 3800 rpm WOT on a 3,000 hour engine that has NEVER been run close to 2,800 rpm? Also, what approach if the seller refuses to do so, other than the obvious prospect of a serious price reduction?

You won't get there man... I'll bet the most you can get out of her is 3000.... Probably overpropped for WOT, but great lower RPM performance... This is the way I personally prefer my boats... But it again is a personal preference....

The surveyor we work with observes WOT while monitoring temperature, rpm, boat speed and visuals on exhaust, but for peace of mind, we will likely pull in a marine diesel mechanic for a more comprehensive engine survey to include dry & wet compression tests. Any recommendations for a trained, experienced and conscientious marine diesel mechanic in the Port Canaveral, FL area?

Since the fluids are due for a change (with a known number of hours and duration since last changed), we will also have them pulled for analysis at Blackstone Labs.

With appreciation,

Matt

Originally Posted by Cheechako

I wouldnt worry about glazing with that use, as long as there's a decent load on it , it's not going to glaze..in fact, it may be more excessively loaded at that rpm if overpropped. But carbon is possible... especially in the exhaust elbow. 1800 seems pretty low even for me who might rather be at 2300! my preferred number here too
If you can get a sense for how much (or any) oil it's burning, removing the head and rebuilding/decarboning isnt the end of the world. (if it even is a problem.... which isnt a given)
He must be way overpropped if he's happy running at 1800 rpm.... so you may not be able to run the engine at 3000+ in testing.
It's just hard to say really.
The turbo may scare me more. Another angle or two: 1)He's lying about the rpm and the engine exhibits problems at higher rpm. 2) or the engine is really like a low hours engine because at 1800 rpm it's only had what... maybe 60% or the revolutions of a 3000hours 3200 rpm engine!

cheech agrees with the possibility of what I'm thinking as I said above...

His other point of having a problem at higher RPM is possible, but I doubt it... Run her at WOT for a while... see what you got... I bet it's the "just broken in" engine I think it is...

[Matt Y]

HappyMdSailor and others, thanks for the perspective. I spoke with two long-time Yanmar service center owners today to obtain pricing to address some deferred maintenance on the same engine. I shared our concerns regarding the risk of bore glazing/ polishing from the 1800 rpm operation, and both said not likely an issue. Both said WOT would tell a lot. One of them will conduct the engine survey. Will report back...

[mub]

Having just rebuilt the turbo on my perkins engine I will give you the "wisdom" from my turbo guy.

My turbo had 3000 hours over 20 years. Its failure was due to corrosion in the exhaust from short running the engine (docking).

The other turbo killer is post shut down heat soak - which cooks the oil in the turbo leading to bearing failure.
He suggested having the clean out 'burn' at the beginning of the use day rather than the end. Idle for as much as a minute then clean it out.

When you have the exhaust elbow changed have them look at the turbo exhaust side for corrosion and feel for wobble.

Mub

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