Race the engine for 5 mins. Does anyone do this?

I've heard diesel engines like heat. I understand. We're traveling the loop and drive 4 to 6 hours at around 1800 rpms. Some say you gotta run the engine up to 80 percent for about an hour to burn out the carbon. I try to comply. Usually with 30 mins or so to go ill run the engine up to 2600 or 2700 rpm. Max is 3400. This makes a huge wake and burns tons of fuel. This makes no one happy. BTW boat is a MS400 and single engine is a Yanmar 6lya-stp 370hp.
Now I read in the manual the you should race the engine up and down for 5 min before shutting down. This is copied from a Yanmar manual.

When operating the engine at low speed for long periods of time, race the engine once every 2 hours.

How to Race the Engine
Repeat a cycle of high speed and low speed operation about 5 times at no load with

the clutch (marine gear) in Neutral position.

Engine racing removes carbon deposits from the cylinder and the tip of the fuel

injection valve.

If racing is neglected, the exhaust color may worsen and performance may drop.

3.3.5 Stopping the Engine

Stop the engine according to the following procedures:

1) Shift the remote control leve to low engine speed and handle to Neutral position to stop the

boat.

2) Be sure to race the engine before stopping. (See 3.3.4-(7).)

3) Operate the engine at low speed (approx. 1000rpm) for about 5 minutes to decrease the

engine temperature.

Okay, anyone do this? I've never heard boats racing their engine after pulling into a slip.
Also, it doesn't say how many rpms for how long.
Thoughts?

I run it up just long enough to burn off the oil, when it quits smoking I drop back down to my normal rpm's. I troll for salmon a lot, at very low rpm's, so once every couple of hours I drop it out of gear and run up the rpm's to burn it off.

I understand that the newer common rail engines don't require this... watching the thread!

I have been told, Cummins 380QSB, never run WOT for more than an hour.
Never heard of racing the engine..... unloaded. If you are tied to the dock, put it in gear and stretch the dock lines WINK

I have been a believer than running up under load is better for an engine that unloaded but I'm no expert by any means.
I cringe when anyone runs an auto, truck outboard or inboard up to high rpm sitting still. I'm a believer in not idling long, start up, get underway and increase rpm as temp increases.
After running at 1800 rpms I do try to run our Yanmar 6LYA up to 2700 - 2800 rpm periodically even if for 15-20 mins.

Personally I would just do what the owners manual says to do. They built the engine so they should be the experts on the engine.

OK, I'm not an expert..BUT.. I don't like that/those ideas.

Did you read it in the manual for yourself or is it just hearsay?

I don't believe these things until I see them for myself.

pete

This takes Yanmar down a notch if not several.
Running WOT in neutral for a few seconds checks the limit governor and perhaps other things but it should only be done once a year or when needed per mechanic or similar.

Running WOT in gear checks many things and after running for a minute or so no problems and good performance is a good safety procedure. Engine should be completely warmed up and inspected thoroughly before the test. It is a test.

Beyond that proper warm-up should be performed and the engine run between 40-45% load and about 75% load. One should stay within that range.

Racing is a bad word to use by an engine manufacturer telling owners how to run their engines. And racing a trawler should not be done ever. But it wouldn’t hurt a good engine for a minute or so.

“Racing” ???

I've read the same. It makes me wary, but I comply. Once we tie up, I de-clutch, and"goose" it once, quickly, to 2500-3500 (wot on our yanmar 4jh3-tes is 3800). Then it idles for 5 mins, then shut down.

I don't feel great about it. They do smoke on startup and I think it's oil puked into the turbo during the shutdown procedure, but I can't prove it.

I refuse to do a turbo wash, per the yanmar manual. That just seems like insanity.

AKDoug said:

I run it up just long enough to burn off the oil, when it quits smoking I drop back down to my normal rpm's. I troll for salmon a lot, at very low rpm's, so once every couple of hours I drop it out of gear and run up the rpm's to burn it off.

I understand that the newer common rail engines don't require this... watching the thread!

Click to expand...

When you rev it up? WOT? How long? 1 min? 5 min?

Bacchus said:

I have been a believer than running up under load is better for an engine that unloaded but I'm no expert by any means.
I cringe when anyone runs an auto, truck outboard or inboard up to high rpm sitting still. I'm a believer in not idling long, start up, get underway and increase rpm as temp increases.
After running at 1800 rpms I do try to run our Yanmar 6LYA up to 2700 - 2800 rpm periodically even if for 15-20 mins.

Click to expand...

Me too. Thats what I try to do. Never heard of racing engine in neutral but that's what manual says.

Pete Meisinger said:

OK, I'm not an expert..BUT.. I don't like that/those ideas.

Did you read it in the manual for yourself or is it just hearsay?

I don't believe these things until I see them for myself.

pete

Click to expand...

That's why I put the pic of manual. Here's the page.

Nomad Willy said:

This takes Yanmar down a notch if not several.
Running WOT in neutral for a few seconds checks the limit governor and perhaps other things but it should only be done once a year or when needed per mechanic or similar.

Running WOT in gear checks many things and after running for a minute or so no problems and good performance is a good safety procedure. Engine should be completely warmed up and inspected thoroughly before the test. It is a test.

Beyond that proper warm-up should be performed and the engine run between 40-45% load and about 75% load. One should stay within that range.

Racing is a bad word to use by an engine manufacturer telling owners how to run their engines. And racing a trawler should not be done ever. But it wouldn’t hurt a good engine for a minute or so.

“Racing” ???

Click to expand...

Um?

Gabe

Gabe n Em said:

I've read the same. It makes me wary, but I comply. Once we tie up, I de-clutch, and"goose" it once, quickly, to 2500-3500 (wot on our yanmar 4jh3-tes is 3800). Then it idles for 5 mins, then shut down.

I don't feel great about it. They do smoke on startup and I think it's oil puked into the turbo during the shutdown procedure, but I can't prove it.

I refuse to do a turbo wash, per the yanmar manual. That just seems like insanity.

Click to expand...

I hear you but it says up and down for 5 mins. How long up? and down? is my question. 5 mins reving an engine up and down sounds crazy. Japanese to English? Lost in translation?

Pmcsurf1 said:

GabeI hear you but it says up and down for 5 mins. How long up? and down? is my question. 5 mins reving an engine up and down sounds crazy. Japanese to English? Lost in translation?

Click to expand...

To be fair- Thats not what it says.
Rev up / down 5 TIMES
Then run at 1,000 rpm for 5 MINUTES to cool engine

Bacchus said:

To be fair- Thats not what it says.
Rev up / down 5 TIMES
Then run at 1,000 rpm for 5 MINUTES to cool engine

Click to expand...

You are correct. My bad. 5 times not 5 mins.

Hopefully our friend Ski will chime in

L

After reading the manual page here is what I think. However note I'm not a mechanic so just amateur thoughts.

They say NOT to shut down after a long/high speed run (i.e. no cool down).

What I have read here before, which makes sense to me, is that most of us will have run up to speed at some point during the day, but then do run at a reasonable length of time at low speed with almost no load (coming in to the marina or anchorage, maneuvering, etc.). That seems like it would take care of the "don't shut down immediately after high speed."

So that leaves the brief "race" before cool down and shutting off, which is your original question. They say it's to remove carbon deposits. So, if you had made a high speed run earlier, are there any to remove? Is this only for people who have trolled all day with no speed run?

It sounds analogous to that quick "rev" that people of my parents' generation always did to their cars before shutting them off. You know, put it in Park, hit the accelerator and a quick "vrooom!" and then shut it off. Those were gas engines, but was there some basis for it?

I guess at the end of this post, I have the same question as you. Is there a benefit to these quick "vrooms"? Do they need to be done if you had already run at high speed during that day (but then idled into the marina or anchorage). Is it a good idea, a neutral one, or a bad one?

(I don't see this as them recommending a long period of high RPM's. I interpret it as quick bursts a la the parents and the car.)

If it were my engine I would (in addition to posting here, which is a good idea) contact Yanmar and see if they can flesh it out a bit. Does it need to be done if you have already run at high speed? What are the downsides? Etc. I'd probably also call a trusted Yanmar mechanic to get their take. Wording my questions so as not to "lead" one way or another.

Pmcsurf1,
Can’t read it w big i-pad too.
I assume you’re showing that Yanmar actually said that ... racing the engine.
What I said in post #7 did not include considerations for turbochargers. Sorry.
But what Yanmar said seems applicable to turbos. But I know little about turbos.
It would probably be good advice if one was to read it w/o the racing bit. Why couldn’t they just say something like “advance the throttle quickly to full throttle for two about one second and then back to idle five times” or whatever.

Edit;
I see Frosty wrote;
“ It sounds analogous to that quick "rev" that people of my parents' generation always did to their cars before shutting them off. You know, put it in Park, hit the accelerator and a quick "vrooom!" and then shut it off. Those were gas engines, but was there some basis for it?”

Perhaps people were thinking if an engine was “loaded up” (too much fuel) a blast of throttle would clear it out. Probably not. When the revs hit their high point .. if the ignition was turned off just then the high vacuum in the entire intake tract would suck in lots of raw gasoline. Not good. And while the engine was shut off the fuel on the cylinder walls could wash much of or most of the oil there-on. Not good.

I had totally forgotten about that Frosty.

Nomad Willy said:

I assume you’re showing that Yanmar actually said that ... racing the engine.

Click to expand...

Whether or not the procedure is always needed (or even desired), I'm pretty sure they just mean "revving" as we'd say it in (North American) English. To me (US), racing would be for a longer period of time, and they do say quick bursts, which I would know as revving. "Rev it up a couple of times." "Okay."

When operating the engine at low speed for long periods of time, race the engine once every 2 hours.

Click to expand...

Me-thinks that's the important bit.

I don't think they are talking about when you are running your boat normally...they are talking about when you are operating at a very slow speed, like trolling for salmon, or if you are charging your batteries at anchor at (or near) idle.

Trouble comes from trawlers liking hull speeds and turbos needing to spool up and clean out. My mechanic says run the Cummins hard for 10 minutes before returning to the berth.

Our manual for our little 30hp non-turbo Yanmar, a 3YM30, provides the same instruction. It is our wing or auxiliary or get home engine. We run it when arriving to a marina, and when loafing along at a few knots, so it gets exercise. I follow the guidance before shutting down.

The usual reason for slow running a turbo before shut down is to lower the turbo temperature enough so the oil in the bearings will be cool enough not to coke.

Read this by Steve: https://stevedmarineconsulting.com/the-perils-of-chronic-under-loading/

I have been in the habit of running my motors up to full throttle every 40-50 hours of run time. I normally cruise at 1400-1500 rpm. The last time I did this at various higher rpms for about 20 minutes. No black smoke, but my fuel burn went from 6gph to over 8gph for the total between fill ups! Don't think I will do more than a 2-3 minute run up in the future. BTW, I have twin Cat 3208TAs.

Cheers, Bill

I would not put too much faith into that part of the manual. In my past engr career I wrote parts of manuals for various machinery (including large diesel gensets) and it was amazing how little oversight there was over what I wrote. Sometimes the task was given to me as it was boring and I was the junior guy. Sometimes I had to do a revision and in reading it there was stuff that did not make great sense, but to make the task simpler I would leave that bit alone. And then you have the Yanmar manual that was clearly translated from Japanese, and I have had many examples where I am an certain the translation was not well done.

My general rules for care and feeding of marine diesels from over 25yrs in the business:

1. If you run light load much of the time (as most trawlers do), once a day or so put it under a good load (80 % of max rpm is fine, no need for full power) for at least a few minutes to burn off carbon and oil slobber. You usually get a burst of smoke on power up, once exhaust is clean, so are internal engine bits. If exh is clear in a minute, run at power for at least five.

2. Cooldown prior to shutdown: There are lots of thermal gradients in engine parts when under a load. Pistons, heads, turbos, etc. When running under a heavy load, you want to run engine unloaded for like five minutes before shutdown. Longer for big engines, shorter for little ones. Fortunately for marine diesels, this is handled automatically buy maneuvering to get in a slip or getting anchored up. More of a concern for engines in other applications where a hot shutdown might be more convenient. For us, not a concern. Except maybe gennies, seen many shut down hot, good to give them a few minutes of run to cool down after taking off the load.

3. Warm up/cool down: Don't go to high load until engine is warmed up. Add load gradually when starting from cold. Actually good to add load and remove load gradually even if warm, if practical.

4. Idling: Minimize how much time your engine is at dead idle. There are lots of places on the engine where lubrication is either splash or otherwise marginal. A few more rpm improves things. Mine idles at about 500, once I start it and oil pressure comes up, I run it up to about 800 til ready to go in gear, then back to slow idle. Same with waiting on a bridge, bump up to like 800.

Note: this does not apply to fishing. When fishing I run the engine where I need and it does what it is told. Usually for me that is like 600. Engine is happy when it knows we are fishing so I know it will not harm itself.

5. Shutdown: I usually rev the main engine to like 1200rpm right before shutdown. This is to throw lube oil all over the place internally. Back to idle for like ten sec for turbo to spool down, then off.

None of the above guidelines are that important. I have been around many engines where the duty cycle was brutal, and the engines did fine. But if you can follow them, I think they are somewhat helpful.

Ski
Thanks for weighing in.
I think many of us have been looking for your insights and experience.

I don't fish with my diesel cruiser but hope mine our equally happy when cruising in new and beautiful places?

A full hour at full load is not good or advisable just allowed. People confuse allowed for required and perhaps that occurred here from the Japanese. Do what Ski said, a few minutes at wot occasionally when convenient not every time. You are not running especially slow. IMO they mean idling. personally

I rarely ever ran at WOT except for a brief test from time to time to make sure all was well. IMO 80% or normal high cruise is all that is needed for any carbon removal.

racing the engine in neutral is not required either IMO. A short period of slow running after full load operation is advisable for cool down rather that a sudden shut down but that usually happens while docking.

My cruising speed of 7kn is 70-75% of WOT. I don't do much else.

I spoke to a Yanmar tech who said to run it at 3000-3500 rpm periodically. We usually do this on a calm day for 20 min or so. I prefer to run it a a lower speed due to the volume in the pilothouse.