Yanmar 4JH4 1000 hour service

CarlN

.
Jan 4, 2009
603
Ketch 55 Bristol, RI
My four year old 4JH4 HTE has reached 1000 hours. It's running great. No smoke. Doesn't burn oil. Coolant temperatures the same as day 1. Same top RPM as day 1.

While I change oil, filters, impeller, and coolant religiously - everything else is original.

I'm a big believer in "if it ain't broke, don't fix it" when it comes to diesels. I've had my share of Yanmar mechanics who have made things worse by touching the engine. Even one who put a part back on the wrong way around.

So. Are any of these "must do"?

- Replace mixing elbow (again, no sign of overheat. No drips. Full RPM)
- Check injector spray pattern
- Check fuel injection timing
- Adjust valve clearance
- Clean turbocharger
- Replace all water and fuel hoses (I'm not going to do this but the manual says every two years)
 
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
Hi Carl, wow, quite the suggested rigorous schedule. Our 1991 boat has a 4JH2-TE, very much like yours. The engine has a bit over 1,900 hours. It had a little over 600 hours when we purchased her in 2002, and have yet to replace the sea water impeller, check injector spray pattern, timing, etc., etc., etc. I do change the oil and filter every 150 hours and the fuel filter periodically, but that's it. She always starts and purrs like a tiger.
 
Oct 1, 2007
1,856
Boston Whaler Super Sport Pt. Judith
My four year old 4JH4 HTE has reached 1000 hours. It's running great. No smoke. Doesn't burn oil. Coolant temperatures the same as day 1. Same top RPM as day 1.

While I change oil, filters, impeller, and coolant religiously - everything else is original.

I'm a big believer in "if it ain't broke, don't fix it" when it comes to diesels. I've had my share of Yanmar mechanics who have made things worse by touching the engine. Even one who put a part back on the wrong way around.

So. Are any of these "must do"?

- Replace mixing elbow (again, no sign of overheat. No drips. Full RPM)
- Check injector spray pattern
- Check fuel injection timing
- Adjust valve clearance
- Clean turbocharger
- Replace all water and fuel hoses (I'm not going to do this but the manual says every two years)
I have a 4JH4E (I believe same as yours but not turbo) with about 900 hours. In addition to the normal maintenance I had the mixing elbow inspected around 500 hrs and the heat exchanger removed and cleaned at around 800 hrs. I reset the valve twice since new. I have done nothing with the injectors or HP pump. Runs perfectly, starts instantly, and runs exactly as it did 10 years ago.
There is an important caveat though. I have a generator and use it every day on cruise to keep the batts topped. My engine idles only when warming up and cooling down. No long periods of idling to charge batts.
 
Oct 22, 2014
20,992
CAL 35 Cruiser #21 moored EVERETT WA
I'm a big believer in "if it ain't broke, don't fix it"
:plus:
And I'm running a 1973 Perkins with unknown hours, Previous Owner maintenance highly questionable, yet she is taking a licking and keeps on ticking.

At some point does it make since to do the basics and then let her run til she needs to be replaced? Just asking.
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Valve clearance check and set if necessary.. On the GM series, Yanmar recommends every 300 hours.. If you've not seen it done or done it, I would do that.. simple and the only one on the list that can do irreparable harm (OK hard to repair then) to the engine.. and displays no really noticeable symptoms until the harm is done.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
I would take a look inside the U-Mixing Elbow every year or two to make sure fouling doesn't close the hole too much.
As for injectors, if it ain't broken...
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
So. Are any of these "must do"?

- Replace mixing elbow (again, no sign of overheat. No drips. Full RPM)
- Check injector spray pattern
- Check fuel injection timing
- Adjust valve clearance
- Clean turbocharger
- Replace all water and fuel hoses (I'm not going to do this but the manual says every two years)
You will find inspection and service of turbocharger and exhaust elbow in these motors takes a while but that is no reason why you would not do so at the intervals Yanmar has published. The rest of your list is pretty straight forward. You say you have checked the manufacturers operator manual. Is there some reason that you think these published service intervals are wrong?

Incidentally - a defective seawater mixing section (elbow) is certain death for your turbo charger - expensive and inconvenient if you are out cruising.

Charles
 
Last edited:
Jun 15, 2012
694
BAVARIA C57 Greenport, NY
I have the same engine. I remember reading in a Yanmar manual that the mixing elbow is either stainless or bronze. Does anyone know if this is correct?
 

CarlN

.
Jan 4, 2009
603
Ketch 55 Bristol, RI
A Yanmar mechanic in Florida who I trust completely (unfortunately I'm not near him), told me he believes the Yanmar manual is now more the work of lawyers than engineers. His example was the manual's requirement that the mixing elbow be replaced (not just checked) every 500 hours (Some colorful language was used for emphasis). He said the design of the mixing elbow on my engine is excellent ( unlike many other Yanmar models) and is not prone to clogging as long as you don't idle too much. Of course, the day has to come -- maybe I will take a look.
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Carl

I cannot follow this. Your trusted mechanic says lawyers substitute their views for engineering standards. Is your mechanic willing to list a maintenance schedule that - but for the lawyers - is better? If so - is he willing to explain why his schedule is superior? If the lawyer schedule is inferior - one assumes this means too frequent maintenance intervals - then your trusted mechanic sure ought to be wiling to explain why less frequent intervals are better.

If he is serious about what you claim he said - then have him call me and we will discuss the matter. I am pretty sure I will be waiting for his call for a very very long time coming.

Charles
 
Last edited:

dLj

.
Mar 23, 2017
3,373
Belliure 41 Sailing back to the Chesapeake
Charles, I think you have it backwards? The lawyers view is far more conservative than the mechanics view on this one. If you follow the maintenance schedule of the lawyerized (wow spell check is actually letting me get away with that invented word) version of the manual, then you won't have problems for sure. The mechanic is correct, you can inspect at the interval suggested, if you see a problem, then act. But the lawyerized version says just replace it. That, of course, allows that any errors on the part of installation free the company from liability. Inspection can be subjective, and hence allows for a greater liability to the company if something happens and inspection had been documented...

dj
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
The problem here is completely obvious -- the mechanic is transferring arguably fair criticisms applicable to the GM style elbows (none have turbos) to the JH turbo series which are not the same motor designs by miles.

Elbows aside - as to the rest of the list I cannot find any other interval that is even arguably premature. Elbow service intervals have nothing to do with injectors or the high pressure pump timing


Charles
 
Last edited:

SG

.
Feb 11, 2017
1,670
J/Boat J/160 Annapolis
I have the same engine. I remember reading in a Yanmar manual that the mixing elbow is either stainless or bronze. Does anyone know if this is correct?

Mixing Elbow - SS vs. Bronze? I'm not sure about the 4JH4, which is the current model. However, we have the Yanmar 4JH2 - DTBE - 88 HP Turbo Charged Diesel which is 19 years old with over 2,500 hours. (It's the prior model.) There were two options, the better one is the bronze mixing elbow because it supposedly resists getting plaqued-up.

We replaced our elbow last year because it had a hidden crack. Cause of the crack could be any number of things.
 
Jun 11, 2011
1,243
Hunter 41 Lewes
I purchased an elbow for my 4JH4 from Mack Boring in NJ, they are an authorized Yanmar dealer and service center. Someone ordered a bunch of motors and they came with the marine exhaust elbow installed. Said customer wanted them removed and credited and now Mack Boring is selling them cheap. They are new but have washer marks as they were factory installed on a new engine, they have no run time on them.
 

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
I have a new to me 4JH4E.... 2005 with 550 hours. Engine runs great.... all original hoses and basic maintenance done. I am changing all engine hoses based on age. Will check valve clearance also.... along with typical maintenance of engine and transmission oils and filters. Mixing elbow on this engine is far better than the HM model I had, but will take exhaust hose for use to check. Small price to pay for peace of mind.
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Replace all water and fuel hoses (I'm not going to do this but the manual says every two years)
Wow, every two years? How about every twenty, for me? I'm embarrassed. But two years seems a bit aggressive.

I would say that for many of the items you list, a good inspection and replacement if indicated routine would be fine. For example, the mixing elbow can be removed and inspected. The turbo, I don't know anything about. Valve clearance can be measured, or course, but it might cost you a valve cover gasket, and as long as you are inspecting, you might as well be adjusting.
 

CarlN

.
Jan 4, 2009
603
Ketch 55 Bristol, RI
I don't like to waste money on unnecessary maintenance. Despite going to the Mack Boring diesel engine class (which I recommend highly), I only do oil/filter and impeller changes myself. The rest I leave to a Yanmar mechanic who I trust - the problem is that the one I trust the most is a long way away. Hate to break in a new one.

Replacing parts to the Yanmar manual schedule is expensive. The manual is very clear that checking the elbow isn't enough - it must be replaced each 500 hours. Using a non-Yanmar elbow is also unacceptable. If I followed the manual exactly, I would have replaced the mixing elbow and the hoses twice by now - probably $3-$5k done professionally. I think there's plenty of justification for questioning the manual.

The Yanmar lawyers recommendations are partly to minimize warranty expense. A good way to do this is to replace parts early - especially those where bad owners can mess it up. As most of us know, running an engine too cool can clog a mixing elbow very quickly. I believe the manual is a "worst case" owner.

The reason I don't expect a problem is that the engine is run to what I was taught at Mack Boring. I don't let this engine idle for long periods for fishing or battery charging. After a careful warmup, it spends most of its time at 2200 RPM which is the sweet spot for this engine according to Mack (max torque) with an occasional full RPM exercise. At shutdown, I rev the engine in neutral three times to blow any excess oil out of the turbo and elbow and then let it wind down for a minute or two before hitting the stop button.

Still, thank you all for your advise. The valves clearance has been checked twice but doing it again is probably worth it - I'm just nervous the new guy will screw it up. I once had a certified Yanmar mechanic at a top boatyard change the oil leaving it a quart low. I will also have the mixing elbow pulled to take a look but I'm expecting it will look fine and not be replaced. It will be interesting to see what I find when the elbow comes off.
 
Last edited:

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Depending on the elbow configuration, you might be able to bore-scope it, take a look inside without completely removing it. Borescopes for smart phones are dirt cheap.

Hoses and be palpated to determine condition, as well as being thoroughly inspected.
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
You have apparently made up your mind and decided to use the old mixing elbow.

But for the rest of us -- these things don't announce they are going to fail because normal corrosion failure is internal and so is quite invisible. You can't see the state of this decay even if the part is removed for inspection. When a failure occurs you will be using the motor. These do not fail when the motor is sitting idle so it is bound to happen at the least convenient moment. These things are plenty cheap. And considering the proximity to the exhaust valves and the turbocharger (both very expensive things) one wonders whether taking a risk is worth the pennies you save by trying to squeeze out the last few hours beyond the 500 hour useful life.

Anyway good luck - but remember you are going to have to replace it sometime no matter what.

Charles

ps Injector spray pattern/pressure and injector pump timing don't need to be done until 3000 hours.
 
Last edited:

SG

.
Feb 11, 2017
1,670
J/Boat J/160 Annapolis
Isn’t the failure of the mixing elbow two different issues? Cracking or deterioration due to corrosion or vibration; and, plaque buildup due to “calification-like” obstruction of the flow?

It usually isn’t without warning, if you are checking for leaks and watching engine temp, especially at higher rpm’s and loading.