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Old 03-12-2011, 06:08 PM   #41
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RE: Can large diesel engines be run at minimum RPM continually?

This is the keel of the AT 34.* Is this what you mean by fairing (the tapering of the terminating end of the keel)?*
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Old 03-12-2011, 06:44 PM   #42
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Can large diesel engines be run at minimum RPM continually?

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
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Old 03-12-2011, 08:45 PM   #43
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RE: Can large diesel engines be run at minimum RPM continually?

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.
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Old 03-21-2011, 06:18 PM   #44
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Can large diesel engines be run at minimum RPM continually?

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
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Old 03-21-2011, 08:12 PM   #45
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RE: Can large diesel engines be run at minimum RPM continually?

Quote:
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
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
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Old 05-19-2011, 10:30 AM   #46
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Can large diesel engines be run at minimum RPM continually?

Quote:
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.
*
Quote:
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.
I suppose many of us worry to much.


-- Edited by markpierce on Thursday 19th of May 2011 10:35:51 AM
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Old 05-19-2011, 01:27 PM   #47
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RE: Can large diesel engines be run at minimum RPM continually?

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.
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Old 05-19-2011, 02:39 PM   #48
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RE: Can large diesel engines be run at minimum RPM continually?

Tom,

What's it have to do with large engines?
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Old 05-19-2011, 03:19 PM   #49
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RE: Can large diesel engines be run at minimum RPM continually?

Quote:
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...
*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"

Iīll 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-3īs, turboed & aftercooled "350 or 255 Cīs".. 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 rpmīs 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.......

Iīll 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 QSBīs ( 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>
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Old 05-19-2011, 03:53 PM   #50
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RE: Can large diesel engines be run at minimum RPM continually?

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".
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Old 05-19-2011, 04:22 PM   #51
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RE: Can large diesel engines be run at minimum RPM continually?

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.

*

*
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Old 05-19-2011, 04:28 PM   #52
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RE: Can large diesel engines be run at minimum RPM continually?

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?
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Old 05-19-2011, 07:47 PM   #53
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Can large diesel engines be run at minimum RPM continually?

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
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Old 05-19-2011, 08:10 PM   #54
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RE: Can large diesel engines be run at minimum RPM continually?

Quote:
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.
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 6BT210īs

Have been real close to #īs 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>
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