Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 30-05-2009, 19:00   #31
Registered User

Join Date: Sep 2007
Location: Colombo
Posts: 1,059
Well after reading all the above I find that I have the answer - just don't run one's diesel at all . Guaranteed to have no wear from friction at all.

In a perfect world one would strive to run the engine at some narrow rev range shown by exhaustive independent tests to be the most economical as far as wear and fuelling is concerned.

But in the end we have to use the engine as we find that we need to do and I suspect unless one is of a particularly anal nature that is what we should do and not worry about it.

Some comment has been made that diesels should be worked hard - that is contrary to the very analytical fleet owners I have worked with when it comes to specifying the performance of their new builds in order to maximise reliability and time between major overhauls. And that is with commercially rated engines, so are much more conservatively rated in the first place than pleasure rated ones. If you make a practice of driving a pleasure rated engine hard you will kill it (and there seem to be plenty of cheap end sail boats coming out with dinky little engines which struggle to power at hull speed against wind and seas).

Certainly engine trials involving idling at the dock are of no consequence whatsoever, especially if one assumes that they are conducted as part of the maintenance of the engine the purpose of which is to preserve its life.

Quote:
Originally Posted by anjou View Post
Idling your engine whilst you top off the batteries is a waste of time as alternators dont produce full power below 1500 rpm.
That is only correct for poorly designed systems or for higher revving small diesels which may be used in order to save weight or for cheapness. It is very easy to select an alternator which can be pulleyed to put out at least very close to full output at idle and otherwise full output at only a hundred or so revs above that for any engine of max. revs around 3,000 or so without exceeding the maximum top end revs allowed for the alternator. For slower revving engines (not so common in modern smaller sail boats in the search for more power from lighter engines but are found in bigger) one can always select and pulley an alternator to give full output at idle.

Why I mention that is there will definitely be much more wear running an engine at low load at high revs for charging compared to running it at low load for the same length of time and the same quantity of charge at low revs and this can be avoided if it is important to one by informed design.
__________________

__________________
MidLandOne is offline   Reply With Quote
Old 30-05-2009, 19:27   #32
Registered User

Join Date: May 2008
Posts: 1,965
I was one told by a tech from Mack Boring (the East Coast US Yanmar distributor) that it's a great idea to give your engine three quick "gooses" in neutral after a long period of low speed operation. Just a second or two right up to 3000+ RPM. As I remember he said it blew the carbon off the injectors and was also good for the turbo charger (if you have one).

Never heard this from anyone else. Does it make sense?

Carl
__________________

__________________
CarlF is offline   Reply With Quote
Old 30-05-2009, 21:05   #33
Registered User
 
deluxe68's Avatar

Join Date: Apr 2009
Location: Arizona/Rhode Island
Boat: Swan 432
Posts: 581
I work in the facilities department of a utility company, we have 13 diesel generators for our various buildings. The largest being a 7 story office building with a server/data floor. We used to run our generators at idle once a month for 30 minutes, it takes them 15 minutes for the coolant to reach 180 degrees. We were told by our Cummins rep that this is bad because it allows wet stacking to occur. This is where crap builds up in the exhaust. We started to do load banks once a year, basically the engines are run under load until they clear out all the built up crap. We analyze the oil several times a year to watch for contamination. The reps never said anything about cylinder glazing. He told me a local hospital never load banked their generators and after 10 years or so they had one break a rod the first time the engine ran under a load during a power outage.
__________________
deluxe68 is offline   Reply With Quote
Old 30-05-2009, 22:16   #34
Registered User

Join Date: Apr 2008
Location: sydney australia
Boat: samson c-shell
Posts: 52
I have owned and operated earthmoving machinery and trucks for 24 years.As some one has said we start the machines up at 7 am ,idle for 3 or 4 minutes and then push the throttle as far as it will go. these machines are then worked like that untill 5 pm when we finish for the day.we do stop for half hour lunch break.
The trucks will do a million miles before we think about head rebuilds and for the smaller 3 cylinder engines it is normal to get 5000 hrs before we look at trading up to newer machine.I had a kobelco 12 ton excavator with 6 cylinder engine that did 12000 hrs before trading in.
the governer on a diesel is set at the factory,so you cant over rev engine and that setting is the speed that engine should be running at.
so for boat engines in neutral push throttle as far as it will go ,check rev counter, will probably read around 3000 revs for 3 or 4 cylinder engine now when in ahead rev counter should read around 2400 rpm and if not then prop is over pitched.
As with earthmoving gear this engine should be warmed up for a few minutes and then run at 2400 rpm for the rest of the day.
__________________
4900bruce
4900bruce is offline   Reply With Quote
Old 30-05-2009, 22:17   #35
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
Interesting discussion - Here is some more conventional wisdom masquerading as facts - LOL

Glazing - Glazing is the deposition of oil on the cylinder walls that becomes very hard and smooth. The problem with glazing is that the cylinder wall actually has to have some imperfection in it. Honing a cylinder is the process where cross hatching is ground into cylinder walls. The reason you don't want a smooth cylinder wall (think glass smooth) is that the oil doesn't film properly on the wall and the rings can't "scrape' the oil off the wall. This results in excess oil being left on the wall that burns in the combustion cycle. This results in high oil consumption.

To avoid glazing during the break in period many overhaulers recommend not idling the engine beyond the normal warm up times, not operating the engine at full rated RPM for a set period of time and to vary the operating speeds so that the engine sees a variety of temperatures and conditons. This is also part of the process that seats the rings to the cylinder walls although with modern materials in rings and cylnders manufacturers may have different break in recommendations based on the materials used.

Coking - Coking is the biggest concern with idling any engine. Fuels are designed to burn completely at a given temperature and pressure. idling the engine is far below the operating spec of the fuel. The fuel actually has split seconds to burn completely - at 3,000 rpm there are 1500 combustion events per minute or 25 per second, for a 3 cylinder engine that's about 8 combustion events per cylinder per second. Lower rpm and lower temperatures result in the fuel not burning completely or burning too cool. Unburned fuel deposits as coke on injectors and in exhaust cans. It can also deposit on exhaust valve stems and exhaust ports. High rpm, pressure and temperature can often blow out or burn away light carbon deposits. A heavily coked engine can be a problem, however.

Oil Circulation - Almost every recreational engine has a constant volume / positive displacement oil pump. That is the flow is a function of speed. Pressure is a function of resistance in the system and maximum oil pressure is a function of the bypass valve setting. This is a technology that has been around since the earliest internal combustion engines. At low rpm there is low flow and because system drag is fixed a lower pressure results. However, your manual will indicate a minumum oil pressure, usually around 10psi. Oil pressure changes over time. As the system wears, clearances between bearing races, valve components and any precision celarance items increases. When the clearance increases there is a natural escaping of oil from the lube circuit into common areas (the sump, the valve galleys etc) - Ambient and oil temperature and the viscosity of the oil can all impact oil pressure. It is not necessary but the pedantic can trend oil vs pressure over time as one indicator of engine health. Oil SOAP (spectrographic oil analysis program) monitoring can identify metals in the oil. For a given sample the soap results can be meaningless but over time trending oil can be useful and is a common aircraft industry practice.

So my habits for a properly broken in engine are this -

At the dock - Fire up the engine - once oil pressure is stable and the coolant temperature starts to rise - increase to around 1,000-1,200 rpm. This gets our alternator in the charge zone. I have left the boat for up to an hour at this level.

On the hook/mooring - fire up the engine to idle. By the time I have readied the boat to get underway (3-5 minutes) drop the hook and get going. We usually try to preceed any races or events by at least 30 minutes. We will run the engine at about 3/4 power the whole time we are setting sail and goofing around. 5 minutes before the race gun we shut down. When we are going cruising we will probably run 50% power for about 15 minutes while getting underway.

If the winds are great we occasionally run the donk 5 minutes and shut it down.

We also always have occasion at least once a month to motor for at least an hour and often 2 at full power. It is important to work the engine hard periodically. High power operations can take care of coke depostis.

We also change the oil every 3 months regardless of hours made on the engine. Oil contaminants are the biggest killer of any engine. As my father always said - you can't hurt an engine by changing the oil.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 31-05-2009, 05:42   #36
Sponsoring Vendor
 
Tellie's Avatar

Community Sponsor

Join Date: Oct 2007
Location: Hollywood, Fl.
Boat: FP Athena 38' Poerava
Posts: 3,045
Dad was right, oil is the life blood of any engine.

Other than that it's $90 an hour,
$120 an hour to sit and listen about all the wonderful websites you found proving your point. $130 an hour to listen to what your Yacht Club pals told you was wrong. $140 an hour to listen all about the other engine you've owned that ran for forever. $150 an hour to look at all the replacement parts you've found cheaper on the Internet. $160 an hour for feeling your breath on my ear while you look over my shoulder the entire time. $170 an hour to explain what every part is when it comes off, it's purpose and function and why it might have to be replaced and why you can't weld it or reuse the same old gasket. $180 an hour when you call me at home during dinner to ask me why your getting a re-build when your new boat neighbor just told you he had the same problem three years ago and just added Mr. Marvels Majic Radiator Wonder and then it ran better than new until he sold it.
Tellie is offline   Reply With Quote
Old 31-05-2009, 12:14   #37
Senior Cruiser
 
unbusted67's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Islesboro, ME
Boat: Looking for a new boat
Posts: 2,196
Images: 24
Quote:
Originally Posted by CarlF View Post
I was one told by a tech from Mack Boring (the East Coast US Yanmar distributor) that it's a great idea to give your engine three quick "gooses" in neutral after a long period of low speed operation. Just a second or two right up to 3000+ RPM. As I remember he said it blew the carbon off the injectors and was also good for the turbo charger (if you have one).

Never heard this from anyone else. Does it make sense?

Carl
That's what the Yanmar manual says. They say to let the engine idle for five minutes then goose the throttle and shut the engine off.
__________________
unbusted67 is offline   Reply With Quote
Old 31-05-2009, 14:02   #38
Registered User
 
S/V Illusion's Avatar

Join Date: Oct 2007
Location: Lakewood Ranch, FLORIDA
Boat: Alden 50, Sarasota, Florida
Posts: 1,692
There is so much authoratative info already available on the engine mfg's web sites, a great deal of which flatly contradicts what the self-proclaimed experts here would have us believe, that this is almost funny to read. Pictures of heads obviously wiped clean, comparison of truck diesel duty cycles with that of marine engines which is totally different are just two examples of "misleading facts".

If anyone is reading this for the purpose of obtaining sound info, stop and read the mfg's advice.
__________________
S/V Illusion is offline   Reply With Quote
Old 31-05-2009, 16:45   #39
Sponsoring Vendor
 
Tellie's Avatar

Community Sponsor

Join Date: Oct 2007
Location: Hollywood, Fl.
Boat: FP Athena 38' Poerava
Posts: 3,045
Manufacturers advice is alway a great place to start.
But if one were to believe everything a manufacturer had to say my old 75 AMC Gremlin would still have been running strong in 76.
Tellie is offline   Reply With Quote
Old 31-05-2009, 17:46   #40
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
the other thing about referencing mfgr advice...

...is that different diesels need to be treated differently. A normally aspirated Detroit is a whole different monster than a turbo Yanmar.

Understand, further, that not all engines made by the same manufacturer perform the same. My Yanmar 4JH3-TE won't come up to operating temperature while idling, even while charging a high-amp alternator. My last Yanmar, a 4JH2E, warmed up just fine at idle. Even though those two engines were built at the same factory, they wanted to be treated differently in terms of warming up, cooling down, and idling without a load.
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 31-05-2009, 18:10   #41
Registered User

Join Date: Sep 2007
Location: Colombo
Posts: 1,059
Quote:
Originally Posted by Tellie View Post
Manufacturers advice is alway a great place to start.
But if one were to believe everything a manufacturer had to say my old 75 AMC Gremlin would still have been running strong in 76.


And if the manufacturer says one shouldn't run the engine for extended times at idle does one then just decide to never charge the batteries when cruising away from the marina? Of course one could install a generator which will unless a larger boat with high electrical demands cost more in fuel and maintenance than any extra cost for maintenance of an idled small diesel ever will. Else one could go around with the boat looking like a chuck up of the international space station and a 19th Century Dutch landscape but that doesn't come cheap either .

Or, for example, if one just races and so each week does a 30 minute drive out to the course and the same back again so the engine never gets a good warm up run, should one go for an aimless drive around the harbour for an extra hour each race day so's the engine does get a work out? Well maybe one will double the life of the engine but all that has happened is one still only gets the same amount of USEFUL hours out of the engine at the cost of the higher maintenance and fuel used for all the non useful hours run.

In the end I think people show too much anxiety about the matter. When specifying a new boat one can do some things to take the intended service into account to ameliorate some of these matters a little but most do not have that luxury, the boat is as they inherited it from former owners.

In my view one should use the boat and engine for the purpose one intends for the boat and if that means, for example, extensive idling periods for charging because one spends much time away from the dock then thats what one has to do. My view also is and as others have said, look after the filters and fluids (but not to be anal about them) and then use the boat for the purpose you intended for it. One thing I do, but just a personal thing, is run the engine for an hour at least fortnightly against the dock whenever it is unused winter and summer - but that just to ensure the machinery compartment, associated electrics and engine is dry and that all is well so as to endeavour to avoid any precipitous type failure from plain neglect rather than worry about wear.
__________________
MidLandOne is offline   Reply With Quote
Old 31-05-2009, 22:10   #42
Marine Service Provider
 
Maine Sail's Avatar

Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 3,060
Hmm....

Quote:
Originally Posted by S/V Illusion View Post
Pictures of heads obviously wiped clean, comparison of truck diesel duty cycles with that of marine engines which is totally different are just two examples of "misleading facts".
Don,

First if you are going to make a weak attempt at calling me a liar I fully expect you to get in your car sometime in the next week or two with your camera and I will remove the valve cover for you so you can snap a photo, post it and then apologize.

There is NO way to clean a top end like that if it had been poorly maintained. Anyone who's ever rebuilt an engine would understand this. Sorry buddy but you insinuating that I am a liar is just in poor taste..

Second I stated no facts. I stated and gave my OBSERVATIONS based on real world conditions I have witnessed and seen, on the water, in AK and here in Maine.

I even forgot to mention my old Cummins in my commercial lobster boat that I sold with nearly 8k on the clock. Though not excessively idled that engine was full throttle for one minute (to the next pot buoy) then idled for 10-15 while pulling that string then full blast to the next one all day long. On the way home at the end of the day she was fed a good hot supper for about 20 minutes to a half hour. I really don't know what to call that kind of use but it can't be kind to an engine..

My opinion is that idling a marine diesel to top off the batts before bed is probably not the worst thing one can do to a marine diesel. Not the best either. But that is my OPINION and is NOT a fact. I know to idle does nothing to actually help the engine, at all, but I think many boaters do far worse things than 20-30 minutes of a charge idle every now and then if they are doing everything else well.

I never said glazing is a myth or that it glazing does not happen, ever. I also stated and prefaced that my particular diesel, that has been idled, has been idled with a Sea Frost refrigeration compressor plus the alt load. This is not a typical idle load for many boats with 12v refrigeration. You and Gord are who turned my observations into "facts".

I apologize to everyone if you misconstrued my post above into thinking I am suggesting that every one go out and begin idling their engines en infinitude. That was NOT my point at all just that what the OP did is probably not instantaneous death to his engine.

Here are some full size high res photos for Don. Look close and you'll see that nothing had been wiped. This is Shell Rotella every 30-40 hours, with filter, and every fall a double change (single filter) the second change to flush and leave a perfectly clean motor over the winter as you see here. These photos were taken in Feb 2009 when I was cleaning, painting, oreventtative maintenance and repairng a cracked bell housing. Yes I know I go above and beyond manufacturers specs on changes but motors are 10k+ and oil changes cost me about the same as a twelve pack of good beer theses days..

For Don photo - Maine Sailing photos at pbase.com

For Don 2 photo - Maine Sailing photos at pbase.com

For Don 3 photo - Maine Sailing photos at pbase.com

Don you are welcome to come to Portland ANY time and I'll pull that valve cover for you. PM me through SBO and I'll give you directions..
__________________
Marine How To Articles
Maine Sail is offline   Reply With Quote
Old 31-05-2009, 22:19   #43
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,821
I'd like to just go electric drive with a genset for charging.
Problem solved !
Steve B.
__________________
senormechanico is offline   Reply With Quote
Old 31-05-2009, 22:21   #44
Eternal Member
 
Chief Engineer's Avatar

Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
Jeepers creepers......This is getting as bad as a firearms on boats thread!!!!!

Just kidding.
__________________
Chief Engineer is offline   Reply With Quote
Old 31-05-2009, 22:27   #45
Senior Cruiser
 
unbusted67's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Islesboro, ME
Boat: Looking for a new boat
Posts: 2,196
Images: 24
Oh yes most definitely when I come to CF I am looking for people's opinions not facts. If I wanted facts I would go to the manufacturers web sight. I am looking for real world experience. With the exception of the occasional injection of encyclopedic factoids from GordMay I am looking for nothing else, so please don't put people down for offering up their opinions and shiny engines, at least not in a thread I start please. No worries of course.
__________________

__________________
unbusted67 is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is idling an outboard for long periods bad for it? PatrickS Engines and Propulsion Systems 4 16-02-2009 07:58
fg how long ksmith Construction, Maintenance & Refit 13 08-08-2008 13:23
How long did it take? Brandywine Multihull Sailboats 17 18-08-2007 19:23
At long last amendelson General Sailing Forum 2 27-03-2007 12:43
so long tauras General Sailing Forum 4 23-11-2005 09:41



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:06.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.