Running Yanmar up to max RPM every hour or so

[cardude01]

My Yanmar 4jh4-hte (turbo, intercooled) operator's manual says to run the engine up to max RPM periodically. I invariably forgot to do this while underway-- maybe did it twice in 4 days on our last trip. When I run it that fast the vibration and noise is pretty bad, plus I still have a pesky overheating issue when I give it full throttle (temp rises above 180 fairly quickly).

At up to 2600 rpm the temp stays at 180 or below. I usually cruise between 2000-2400rpm (30-40hp out of 110 max hp) for speeds of about 6.5-7.5 knots.

Am I doing damage by not doing this full throttle drill? I think I read I was also supposed to do it before turning the engine off, but I'm usually so preoccupied with not hitting the dock I forget to do then also.

 

[MurrayM]

Are you sure that's what it said?

The operation manual for our 100hp 4JH2-UTE makes reference to something similar, where it states;

"When the engine is operated at near idle speed (below 1000 rpm) for a long time (over 2 hours), excessive carbon and fuel residue tends to accumulate due to incomplete combustion.

Carbon deposits on the injection holes of the fuel injection valve, the turbine blades of the turbocharger, etc. cause a drop in engine output, knocking, and other troubles. To prevent these problems, be sure to blow off the carbon accumulations by full speed operation.

Operate the engine at over 2500 rpm for one minute in every two hours of continuous low idle operation."

As for stopping, our operation manual states;

"To stop engine, place the control lever in "Nuetral" position and operate the engine at low idling speed for about 5 minutes".

Sounds like you're starting at the bottom of the learning curve, which is exactly where I was a little over two years ago There is so much to absorb...a highlighter pen and cheat sheets/lists will be your best friends!

 

[DavidM]

Well, there are several issues embedded in your post.

First, that particular Yanmar may have a little known manufacturing defect that lets it overheat at wot. PM me with your email address and I will send you Yanmar's service bulletin that you may want to discuss with your Yanmar dealer. I doubt that they will remember it if you don't have it in hand ;-).

Secondly, 2,000+ rpm and 30+ hp is plenty to keep that engine up to full operating temps. Think about it, that very same block in normally aspirated form only makes 50 hp, so 30 is plenty.

But almost any engine will build up soot in the exhaust manifold if run significantly below wot. Running it up (but I wouldn't go to wot, 2,800 should be fine) for 5-10 minutes to blow out the soot is a good practice, but not doing it religiously isn't going to hurt anything. But you have to do it in gear. Doing it in neutral won't do the job.

Finally the Yanmar GM and JH engines are notorious for building up soot and scale in the exhaust elbow and plugging up. The most obvious symptom is not being able to hit rated wot rpm accompanied by heavy smoke. If this happens, inspect and if necessary replace the exhaust elbow.

David

 

[cardude01]

Are you sure that's what it said?

The operation manual for our 100hp 4JH2-UTE makes reference to something similar, where it states;

"When the engine is operated at near idle speed (below 1000 rpm) for a long time (over 2 hours), excessive carbon and fuel residue tends to accumulate due to incomplete combustion.

Carbon deposits on the injection holes of the fuel injection valve, the turbine blades of the turbocharger, etc. cause a drop in engine output, knocking, and other troubles. To prevent these problems, be sure to blow off the carbon accumulations by full speed operation.

Operate the engine at over 2500 rpm for one minute in every two hours of continuous low idle operation."

As for stopping, our operation manual states;

"To stop engine, place the control lever in "Nuetral" position and operate the engine at low idling speed for about 5 minutes".

Sounds like you're starting at the bottom of the learning curve, which is exactly where I was a little over two years ago There is so much to absorb...a highlighter pen and cheat sheets/lists will be your best friends!

Im definitely at bottom of the curve !

I went back to the OM and could find nothing about running up to WOT. Guess I dreamt that up.

I did find this about shutdown:

NOTICE: Avoid engine damage. Do not stop engine abruptly during operation. Yanmar recommends that when shutting the engine down, allow the engine to run, without load, for 5 minutes. This will allow the engine components that operate at high temperatures, such as the exhaust system, to cool slightly before the engine itself is shut down.
1. Reduce engine speed to low idle and put remote control handle in NEUTRAL.
2. Accelerate from low speed to high speed and repeat five times. This will clean out the carbon from the cylinders and the fuel injection nozzles.
3. Allow engine to run at low speed (approximately 1000 rpm) without load for 5 minutes.

What does it mean by "high speed"? What RPM?

 

[cardude01]

Well, there are several issues embedded in your post.

First, that particular Yanmar may have a little known manufacturing defect that lets it overheat at wot. PM me with your email address and I will send you Yanmar's service bulletin that you may want to discuss with your Yanmar dealer. I doubt that they will remember it if you don't have it in hand ;-).

Secondly, 2,000+ rpm and 30+ hp is plenty to keep that engine up to full operating temps. Think about it, that very same block in normally aspirated form only makes 50 hp, so 30 is plenty.

But almost any engine will build up soot in the exhaust manifold if run significantly below wot. Running it up (but I wouldn't go to wot, 2,800 should be fine) for 5-10 minutes to blow out the soot is a good practice, but not doing it religiously isn't going to hurt anything. But you have to do it in gear. Doing it in neutral won't do the job.

Finally the Yanmar GM and JH engines are notorious for building up soot and scale in the exhaust elbow and plugging up. The most obvious symptom is not being able to hit rated wot rpm accompanied by heavy smoke. If this happens, inspect and if necessary replace the exhaust elbow.

David

David

You actually sent me that bulletin already, but I have not discussed it with a Yanmar dealer yet. Need to find a good Yanmar dealer around the Bradenton/Sarasota area. Boat will be in that area for a few months.

OK, so run it at 2800 RPM for 5-10 minutes to blow out soot. I guess that's what I was thinking about. Not sure where I got the WOT idea.

Thanks for the elbow tip. Just saw that "clean or replace mixing elbow" is on the 500 hour service. Mine has 580 hours.

 

[Nomad Willy]

cardude01,
Engine coolant temp is controlled by a thermostat and the measured temp is not representative of the temp of many important internal parts like valves and pistons. It takes considerable time to heat soak these parts. My engine quickly gets up to 190 coolant temp .. and only climbs a few degrees at heavy loads.

I personally don't go to WOT very often. I don't do it to "blow her out" as in get rid of carbon buildup. I do it mostly as an engine check to see if all is well. I did it before I bought the boat and for a little longer time just after .. several minutes and then the engine quit. There was a problem and I discovered it by running at full bore. I sold the engine before I found out specifically what the problem was.

Many .. like lots and lots of trawler skippers never run at WOT. They don't know if their prop or rpm at full power is even close to correct. Running for a minute or two at WOT is good preventative maintenance.

There's one situation that running full bore every time the boat goes out is good or even necessary and that's w an over propped boat running very slow. Depending on the speeds and loads it may not be needed. But running an over propped boat at WOT is never good. Actually at certain boat speeds an over propped boat may be running at a more favorable rpm and load than one that is correctly propped.

 

[Xsbank]

The engine is designed for WOT. It has a governor to limit its RPM and it has been rated for a particular operating envelope. For example, my engine, a C series Cummins, is rated M1 or 'continuous' (24 hours) at WOT. Some are rated for 1 hour at WOT out of 8. Overpropped means the engine will never hit the governor so WOT on an overpropped boat means max achievable rpm.

WOT sounds like God's Own Clamcrusher and is quite alarming when you are used to the part-throttle we usually use when we noodle around at low, economical rpm.

WOT is a useful diagnostic tool and will reveal any weaknesses in your cooling system etc., which need to be fixed for reliable cruising.

Diesels don't like to idle, they are not running efficiently there. Diesels like a load.

Read your manual!

You will also read here that many are afraid of WOT, think it does damage or might shorten the life of their delicate diesel.

Read your manual!

 

[BlueYonder]

I had the same recommendation in the manual for my Yanmar 6LY2A.

The procedure described by Yanmar is intended to be done at the dock. Put your transmission in neutral, run the motor up momentarily then back down to idle 5 times. Leave it at idle for five minutes, then shut down.

I would think that if you run the motor at higher rpm for 5 or 10 minutes on your way back to your slip, you will essentially accomplish the same thing. The slow speed back into the marina should provide the 5 minute cooling period.

I had a Yanmar 3GM in a sailboat, the elbow had to be replaced because of soot build up.

 

[DavidM]

Yanmar makes a couple of silly recommendations/statements about their engines. Running the engine up in neutral to blow soot out is one. Saying that you can run their engines continuously at 200 rpm off of wot is another.

The pros who make their living servicing marine diesels over on boatdiesel call these "couch engineer" written recommendations. They have no basis in real world experience.

You need heat to blow/burn off soot and you aren't going to get that heat in neutral, only near wot in gear.

Running continuously at 200 off of wot is purely a marketing statement. It makes the engine look good to put out all of that power continuously but it is written so they won't have to pay off many warranty claims if you do so ;-). But after the warranty period is over, good luck!

David

 

[Nomad Willy]

David,
200 off would be fine if one was underpropped 100rpm.

Never heard of the run it up in neutral 5 times. Seems nuts but running your trawler engine at WOT at times seems nuts to many here. I had a Yanmar that was rated at 3450rpm and running it 200 down seems well into the intermittent catergory. I wouldn't run my Mitsu 200 down but if I wanted to I'd take the trouble to look it up if I wanted to run 300 down. And I would think any engine in good condition should be able to run 400 down. For a Lehman that would be slightly lower than your 85% of rpm suggestion.

Of course engines are rated differently so this should vary. My Mitsu is marketed by Westerbeke as 44hp, Vetus as 42hp and Klassen as 37hp. All however are rated at 3000rpm. Since I'm just a bit overpowered I'll probably never run less than 500 down and I've done that many times.

 

[Phyrcooler]

Regarding overheating at full throttle, when was the last time your coolers were checked/cleaned out? Might be time.

As others advise, a year's membership at boatdiesel.com is worth the investment. Research everything written about your engine, then just start reading all you can about all things diesel, fuel systems, transmissions, etc.

Good learning for all us rookies.

 

[cardude01]

I had the coolers cleaned with "barnacle buster" when the boat was at Ft Lauderdale but it didn't do any good. Still heats up past 2600 RPM.

On David's advice I have emailed a Yanmar service shop that bulletin, and asked if it could be covered under warranty.

Here is a copy of that bulletin if anyone else is having this overheating problem.

 

[DavidM]

Cardude:

Although I haven't done it myself, pulling the tube bundle and rotating the improperly installed shield is a reasonable DIY job. I say this because Yanmar cleverly put some conditions on paying for the fix that are going to cost you some real money whether it is improperly installed or not.

The dealer is obligated to check all of the things that Yanmar requires before pulling the bundle and checking for improper orientation. This serves two purposes: it makes sure that Yanmar doesn't pay for any fouling related overheating, and it gives the dealership some more revenue to do these things before Yanmar kicks in.

If I had one of these I would do it myself. It would cost a few bucks for gaskets and O-rings but that would be cheaper than playing Yanmar's game.

David

 

[cardude01]

David,

I think will DIY the repair when I get the boat back to Texas. I will have more tools and a better facility to do it, and will not be under any time pressure. I was planning on driving up a week before our June Keys trip to replace the batteries and get some other piddly stuff done, but I don't think I will have time to tackle this job. Plus I worry if I get this job started (or break something else in the process) it will screw up our family Keys trip. This heat exchanger is on the most inaccessible part of the engine of course.

There is no overheating whatsoever until I push it up into the higher range RPMs (which I never use), so short term I really don't see a problem.

Do you?

 

[DavidM]

No I do not see a problem if you operate below the point that it starts overheating.

FWIW I discovered this problem after helping a neighbor solve his very similar problem as yours with that engine. The overtemp alarm would go off at 2,600. We cleaned the heat exchanger. It went up to 2,800. We changed the coolant. It went up to 2,900 rpm. But with a squeaky clean raw and coolant system it still would overheat at wot.

After doing all of that I finally saw the Yanmar service bulletin and then it all became clear.

David

 

[cardude01]

????

Thanks

 

[Spottsville]

Thanks for posting the service bulletin. I have one engine doing the same. After I Barnacle Bust it if it still gets hot at high RPM this may be the fix!

 

[Pgitug]

I had the coolers cleaned with "barnacle buster" when the boat was at Ft Lauderdale but it didn't do any good. Still heats up past 2600 RPM.

On David's advice I have emailed a Yanmar service shop that bulletin, and asked if it could be covered under warranty.

Here is a copy of that bulletin if anyone else is having this overheating problem.

View attachment 39078
View attachment 39079
View attachment 39080

HERE IS YOUR ANSWER TO OVER HEATING. I have been there, done that, on my Yanmar four cylinder diesel.
The problem for over heating at lower and lower RPM's is scale build up on your heat exchanger tubes, BUT the scale build up is on the fresh water side! That's why you had no improvement with Barnacle Buster. The fix is easy. But the path to it was not. I looked at everything, thermostat, raw water pump, new hoses, cleaned out the exhaust elbow, bla bla bla.
When I pulled out the heat exchanger tube core I found a clay like coating on the fresh water (AntiFreeze) side of the tubes. I tried cleaning off the clay with acid, soap, cleaners, nothing worked. I went to my local NAPA store and was told that their diesel radiator flush would clean it up without any work on my part. They also said that the early scale build up was caused by using the "Yellow" color AntiFreeze. So I bought their diesel radiator flush and their Purple Diesel AntiFreeze and went back to the boat to follow the directions. Reassembled the heat exchanger, put all the hoses back on and proceeded with the cleaning process which is:
Step 1 Drain engine's fresh water system of all antifreeze and remove the engine thermostat. Reassemble thermostat housing.
Step 2 Pour in the pint container of NAPA's diesel radiator flush.
Step 3 Fill to top with fresh water from your garden hose.
Step 4 Use you boat normally until you have 6-8 hours on the engine.
Step 5 Drain coffee colored water out of engine after engine cools down.
Step 6 Fill with garden hose and run engine for a few minutes, then drain.
Step 7 Repeat step 6 until water drains clear.
Step 8 Install new thermostat.
Step 9 Fill system with Premixed antifreeze. NEVER put in antifreeze concentrate and then fill with water. The concentrate will scale the heat exchanger tubes before it gets a chance to mix.
Now I can run my Yanmar at WOT for even fifteen minutes and the thermostat never reads above 178 degrees, in Florida's eighty five degree water. YEH!

 

[cardude01]

Interesting. Thanks for that update.

 

[Wxx3]

Are you sure that's what it said?

The operation manual for our 100hp 4JH2-UTE makes reference to something similar, where it states;

"When the engine is operated at near idle speed (below 1000 rpm) for a long time (over 2 hours), excessive carbon and fuel residue tends to accumulate due to incomplete combustion.

Carbon deposits on the injection holes of the fuel injection valve, the turbine blades of the turbocharger, etc. cause a drop in engine output, knocking, and other troubles. To prevent these problems, be sure to blow off the carbon accumulations by full speed operation.

Operate the engine at over 2500 rpm for one minute in every two hours of continuous low idle operation."

As for stopping, our operation manual states;

"To stop engine, place the control lever in "Neutral" position and operate the engine at low idling speed for about 5 minutes".

Sounds like you're starting at the bottom of the learning curve, which is exactly where I was a little over two years ago There is so much to absorb...a highlighter pen and cheat sheets/lists will be your best friends!

THis is pretty good advice for virtually any diesel engine.

The cool down period is especially critical on turbo charged engines.

Turning off the engine while having just run at high load, is far worse than any carbon buildup at low rpm's.