Can large diesel engines be run at minimum RPM continually?

Brent,
It's a pdf file and I can't figure out how to post it.
I can't attach it as an image because it's the wrong file type.
It won't "paste".

HELP!

And after really reading your post if your boat is a 1984 tou don't have the exact engine...I had a T6.354 which were discontinued in 1980 (IIRC). You should have T6.3544 AKA "Range 4" engine.


-- Edited by jleonard on Wednesday 2nd of March 2011 01:49:24 PM

this is another one of those "which anchor is best" questions.
* FWIW, before we purchased our current boat, I called Caterpillar (we have 375 hp turbo 3208's) and asked all the questions I was curious about on these engines.* On the question about operating rpm range, the answer was that the engine can be continously operated withing 10% to 100% of it's rated*hp subject to the rating restrictions that Cat publishes (E rating, C*rating etc) providing the engine cooling water temp is 180 degress fahrenheit to 210 degrees, period.* Operation below the 10% can be conducted subject to maintaining the min. coolant temp provided the load is increased periodically (no definition here of the period) to reduce any white smoke or rough running.* They also recommended running up to 80% rpm for 20 minutes out of every 8 hours running at very low rpms.* To translate*hp to rpm you need the cat sheets which are in the manual (also on boatdiesel.com) supplied with the engine.* In my case* 10% on a displacement prop curve is 1200 rpm (I am not displacement but I use this as it is the only thing they produce and at such low speeds I don't think there can be much difference.
They also said my 507 twin disc transmission can freewheel for up to eight hours, as I wondered about running on a single engine, but I haven't had the nerve yet to try this.

jleonard wrote:


Brent,
It's a pdf file and I can't figure out how to post it.
I can't attach it as an image because it's the wrong file type.
It won't "paste".

HELP!

And after really reading your post if your boat is a 1984 tou don't have the exact engine...I had a T6.354 which were discontinued in 1980 (IIRC). You should have T6.3544 AKA "Range 4" engine.


-- Edited by jleonard on Wednesday 2nd of March 2011 01:49:24 PM


PM Sent.* Thanks Jay!

Click to expand...

*

DavidM wrote:

Steve:

I believe that you have the normally aspirated (no turbo) 135 hp Perkins 6.354 engine. The rated rpm is 2,400.**



Hold on....* I have 6.354s and they will turn 3000.* There are many different flavors of 6.354, does anyone know the rated RPM for sure?* Mine seem to be happy at 2100 and cranking them up to 2500 doesn't produce black smoke or excessive heat.* I ran them this weekend at 2900* for a few minutes and other than the boat going very fast and burning a bunch of fuel there didn't seem to be any ill effects.

Woody

Click to expand...

-- Edited by Egregious on Tuesday 8th of March 2011 09:07:02 PM

Have you verified the accuracy of your tachometers?

The old* T6.354 I had was rated at 2400 rpm. That's straight from the book. Mine would turn almost 2700**at WOT even though I was "over propped" by comparison to other like boats.
That was with a calibrated tachometer. (I'm pretty anal about that)


-- Edited by jleonard on Wednesday 9th of March 2011 05:53:22 AM

-- Edited by jleonard on Wednesday 9th of March 2011 06:04:49 AM

jleonard,
You said:
" I was "over propped" by comparison to other like boats." Who gives a squat about other boats? This is w a previous boat**** ...right? Under propped isn't the end of the world if one dos'nt over rev. Actually I prefer to be about 50rpm underpropped. That way you can't get overloaded. 100rpm underpropped is ok too but not ideal at all. Overpropping definitely will burn a bit less fuel but you don't know where (rpm wise) the overloading starts and nobody can tell you. The only thing I like about it is that it's a little bit like installing a smaller engine. Does anybody know the rated rpm for the 330 cu in engine that preceded the Lehman?

"Who gives a squat about other boats? This is w a previous boat**** ...right"

Hey I'm in agreement with you , I was only making a point. That was with my ex, a 34 Mainship model I, 1978 vintage. Performance wise those boats were all very close dependant of course on the particular engine model that they came from the factory with.

But here's something...I was plannning an eventual *repower and using info from a boating pal who had the same boat and had repowered. So little by little I did the upgrades so when I finally did repower the boat would be ready.
Just by fairing the back edge of the keel ahead of the prop I gained 250 engine rpm.
The Mainships had a flat end to the keel and fairing it (by adding a bullet shaped piece) that stopped the water from "eddying" and gave clean water to the prop.
I was then able to add an inch of pitch plus a cup to the wheel.
It was a fun project with positive results

Jay,You've hit on something that will be big stuff for at least several Willard owners. See my picture of the stern of a W30. The flat part of the trailing edge of the keel is quite large.
When I did my refit I wanted badly to reshape the keel but we just didn't have time. As you can see the trailing edge of the keel and the prop are quite close together and can't be faired
in the manner you described. It would be a BIG job on the Willard. But some may want to do it after reading your testimony of increased performance. I would like to post most of your post on the Willard Boat Owners Group * *....with your permission.

Avista wrote:

On the question about operating rpm range, the answer was that the engine can be continously operated withing 10% to 100% of it's rated*hp subject to the rating restrictions that Cat publishes (E rating, C*rating etc) providing the engine cooling water temp is 180 degress fahrenheit to 210 degrees, period.

Click to expand...

That is great information Avista, and conforms to what I was told by a CAT engineer who worked on the 3306 design team.* Said these engines were designed to idle for long periods during Arctic duty so make great trawler engines.* Emission requirements have fundamentally changed the name of the game for small diesel design - some for the better, and some not so much.

*

"with your permission."

Go for it. I have no problem sharing my experiences.

I may have some pictures I took during and after the job. Send an e mail to me at work** jleonard@usa.norgren.com** I have a CD there with some older pictures.

I basically started with a leftover length of 4x4 pressure treated post. Cobbled up a piiece for aboe the prop and one for below.*West system glued*them in place (held with duct tape). Then the next weekend I used my 4 inch grinder and 36 grit paper and shaped the blocks, and ground the boat to make room for 3 layers of 1 1/2 ounce mat and poly resin. Cleaned it up and did 3 laters of gelcoat, bottom paint done.

Not much room on the Willard judging from the picture. You'll have to get creative

This is the keel of the AT 34.* Is this what you mean by fairing (the tapering of the terminating end of the keel)?*

Yes
Picture below

-- Edited by jleonard on Monday 14th of March 2011 06:46:59 AM

-- Edited by jleonard on Monday 14th of March 2011 06:48:11 AM

Eric couldn't wait to call me to tell me about your post,* cause he and I had talked about doing something like this.

I am going to have to cut some holes in my keel back aft so I can get at some bad concrete nd boiler punchings,* so figured to kill two birds with one stone.

I had drawn these lines in magic marker several days ago,* and a friend who is a fibreglass pro is going to help me put it all together,* right in my side yard this spring.

Upon hearing your results I may make my cuts deeper than the lines I drew originally.

Check out the pics.

Dan in Maine

BTW,* Stanley at Beta diesel claims you can run the new Kubotas slow all day long.

this article talks a bit about running engines at low rpm/low load and also some info about how to avoid problems:

http://coxengineering.co.uk/bore.aspx
http://coxengineering.co.uk/oil.aspx


-- Edited by Singleprop on Monday 21st of March 2011 06:23:55 PM

jleonard wrote:

"with your permission."

Go for it. I have no problem sharing my experiences.

I may have some pictures I took during and after the job. Send an e mail to me at work** jleonard@usa.norgren.com** I have a CD there with some older pictures.

I basically started with a leftover length of 4x4 pressure treated post. Cobbled up a piiece for aboe the prop and one for below.*West system glued*them in place (held with duct tape). Then the next weekend I used my 4 inch grinder and 36 grit paper and shaped the blocks, and ground the boat to make room for 3 layers of 1 1/2 ounce mat and poly resin. Cleaned it up and did 3 laters of gelcoat, bottom paint done.

Not much room on the Willard judging from the picture. You'll have to get creative

Click to expand...

instead of p.t wood I woud get ahold of some rigid foam board, grind off the bottom paint from the entire area, glue the foam to the back of the keel, shape it with a shureform tool... then glass it as above. The p.t. woods not a great idea... if it gets wet it could cause some issues. That flat deadwood as shown is a MAJOR cavatation producer
HOLLYWOOD

nomadwilly wrote:
I've been strongly against under loading on this forum for years and I repowered my boat w an engine that I thought was the absolute minimum amount of power necessary to drive my boat.** ...* *Under loading is bad but the bad effects are a long time coming*** ...there will be no sudden death** ..and years of boating fun can be had doing it so it's a bit like eating fat foods like deep fried foods but one will have to pay at some time most likely.

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*

nomadwilly wrote:
Mark,

I think the concept of getting pooped because of a swim step is like the concept of ruining your engine from underloading*** ....it's obvious but it never seems to happen. I don't have a swim step and I don't underload my engine but I know of none that have suffered from it either. If I knew all that went on everywhere that probably would'nt be true. But the above observations don't give me personally the desire to underload or have swimstep.

Click to expand...

I suppose many of us worry to much.


-- Edited by markpierce on Thursday 19th of May 2011 10:35:51 AM

There is a good thread running on boatdiesel about running diesels slow. It all started with some statements Bob Smith made at a recent trawler fest.

On a side note, the recent PMM has an article on a Marlow 57 with Cat C18s that achieves 8.5 knots at 900 RPM while burning 4gph. Oh yeah, the boat will cruise at 24 knots too! That Marlow looks a lot better to me than the long in the tooth Fleming 55s, especially its systems.

Tom,

What's it have to do with large engines?

sunchaser wrote:
There is a good thread running on boatdiesel about running diesels slow. It all started with some statements Bob Smith made at a recent trawler fest...

Click to expand...

*Here's Tony Athens*(SeaBoard Marine)*comments on the thread that Sunchaser referenced.* Interesting.

*
<table style="width:100%;" border="0" cellspacing="0" cellpadding="5" bgcolor="#ffffff"><tbody><tr><td class="L1000" bgcolor="#eeeeee" width="40%">*</td><td class="L1000" bgcolor="#eeeeee" width="20%">*</td><td class="L1000" align="right" bgcolor="#eeeeee" width="40%">*</td></tr><tr><td colspan="3" bgcolor="#ffffff">"Low Speed Running"

I´ll through this in although I have written much on this in the past..

In the last 5 yrs, I have removed at least 12 Cummins engines built between 1999 & 2003 that I had installed in commercial vessels during those years.. Not one had less than 14000 hours and a few were in the 24000-27000 hour range.. All were 6CTA 8.3 M-3´s, turboed & aftercooled "350 or 255 C´s".. Not one of these engines ever pulled more than 150 HP from them during cruise operation and most ran abound at 100-120 HP.. Not one ever saw WOT other that on seatrial day a decade ago, and they never got "blown out" ( well maybe once or twice if I was on the boat troubling something) . They were just run SLOW at rpm´s between 1200 and 1600 RPM for the entire time ( plus lots of idle time too....................Not one new turbo, not one head off, and not one set of injectors on any of them, plus every engine was operating great when removed.......

I´ll put in all a nut shell-- IMO, Low Speed running of these type of engines and all the old wives tales associated with it, is a bunch of crap when the engines are set up right and well maintained.. Remember, I have yet to see and engine fail from "low speed running"..

BTW, I have my first set of QSB´s ( Aloha Spirit, Ventura, Calif) that we watch over is right at 10,000 hours--Where does he cruise at?--4-5 GPH at under 1800 RPM 100% of the time... Only issues? Sherwood seawater pumps.. I saw the Capt yesterday in my shop and he had brought in the on-engine "last chance" fuel filter.. Still had factory paint on it (over 9800 hours)--He wanted to cut it open and the Multi-Stage filters before it, and we did-- The FF5488 was still in good shape at over 9800 hours.. His first filter (mud filter FF5013) - he changes it ever other oil change) was full of a lot of crud & mud as it should be.. The second filter (FS19563 WIF unit) was about 1/4 gone.. He had changed it about 4 times since new................The point here--IMO Multi-Stage Fueltration is the only way to go and low speed running is not a concern..


Tony</td></tr></tbody></table>

Interesting. Our boat may be overpowered (I am sure Nomadwilly will say so) with a Cummins 6BTA 330 (turboed and aftercooled), which we rarely (except for the 20 minute end of day's run WOT "blow out" at a whopping 12.5 to 13.7 knots depending on load etc) operate at over 1,800 rpm. I have followed the discussions here and on other forums ("fora" to be correct say some) on this subject and have been worried about the potential damage I might be doing to our engine running it at this low rpm.

Does this mean I can now relax?

Or is this just a minor dissenting opinion?

Of course, at 100-150 engine hours/year on an engine that has just over 1,000 hours on it, the engine will probably out live me, even if it is being run "too slow".

Larry

In addition to Tony's post, I found Paul Foulston's points on the same thread interesting too. Paul pretty much said Bob Smith's support of "blowing her out" were specific to some older designs and did not necessarily pertain to "modern" diesels. Paul is an encyclopedia on marine diesel foibles during the past 50 years

Best to read the full thread,*keeping in mind Tony Athen's*long held position that he has never seen a well maintained diesel give out due to under loading.

*

*

Tom, when they say you don't need to run up a "modern" diesel, what is the definition of that?* I assume my CAT 3306 mechanical injection wouldn't qualify?

Carl -* Pertaining to the ability to run in the 1400 to 1800 rpm range for long periods, my guess as to* modern diesels referenced by boatdiesel would include mechanical or electronic four cycle light weight*engines designed to utilize a turbo. This list for engines less than 450 hp would include Cat, Cummins, JD, Lugger, Perkins Sabre, Volvo, Yanmar and Iveco made during the past 25 years or so.*Some of these are throwaways and cannot be resleeved thus becoming Rocna competitors.

Your 3306 is modern to me, I've bought*many of them (and their relatives) for gensets and mobile equipment. I believe the 67d series, as it was called, started production in the late 1960s.

For you trivia buffs, Clessie Cummins ran a Dusenberg with a 361 ci four cylinder diesel in the '31*Indy 500*- without a fuel stop and achieving 16 mpg!


-- Edited by sunchaser on Thursday 19th of May 2011 07:56:54 PM

sunchaser wrote:
Larry

In addition to Tony's post, I found Paul Foulston's points on the same thread interesting too. Paul pretty much said Bob Smith's support of "blowing her out" were specific to some older designs and did not necessarily pertain to "modern" diesels. Paul is an encyclopedia on marine diesel foibles during the past 50 years

Best to read the full thread,*keeping in mind Tony Athen's*long held position that he has never seen a well maintained diesel give out due to under loading.

Click to expand...

Sunchaser:* *Here's Paul's post.* I think*he was referring to "blow by"?
<table style="width:100%;" border="0" cellspacing="0" cellpadding="5" bgcolor="#ffffff"><tbody><tr><td colspan="3" bgcolor="#ffffff">I do not know why Bob Smith should be such an authority. When I worked for Ford we thought that Lehman marinisations were at best poor and over complex and not a patch on Sabre who eventually purchased them.

I have been involved over the years with three re-powers of Lehman powered vessels.

#1 Grand Banks 32 Lehman Ford NA 120hp out to Cummins 6BT210
#2 30 foot 12 tonne crabber, Lehman Ford NA 80hp out to Cummins 4BT150
#3 42 foot Taiwan tupperware GB lookalike with pair of Lehman Ford NA 120hp out to pair of 6BT210´s

Have been real close to #´s 1&2 since repowered and did survey on #3 on an ownership change. #1 has over 5,000 hours and #2 well over 11,000 hours. Retired owner of the GB NEVER pulls more than 1,500 rpm, #2 goes out to fishing ground at 1,500/1,700 rpm, idles for an hour whilst pulling string of pots then 1,500 to the next string and and so on. Home at the same speed unless weather suddenly turns bad, then he gives motor the beans.

#2 had blow by check at 9,000 hours, perfect!

#3 Was recently sold, previous owner claimed that 1,400 rpm was real comfortable and very economical, 2,500 hours, blow by once again perfect.

Lube oil control on Ford Dover engine was always a problem for us in engineering, Bob Smith should not judge other makes of motor by old Ford Dorset/Dover standards.

Paul.</td></tr><tr><td valign="bottom">*</td></tr></tbody></table>