Reply
 
Thread Tools Display Modes
 
Old 10-25-2011, 05:22 PM   #21
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
RE: A new and excellent post on underloading

It's not a great idea because you are putting a lot of water and combustion products in the oil to create acids that will damage the bearings. You won't get the engine hot enough to dry out the oil.

You would do better to seal up the crankcase vent, air inlet, and exhaust before the engine cools when you park it and leave it alone until you plan to use it. You can bar it over once in a while if you want to change the position of the rings in the cylinders, that won't hurt anything.
__________________
Advertisement

RickB is offline   Reply With Quote
Old 10-25-2011, 06:45 PM   #22
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: A new and excellent post on underloading

Quote:
superdiver wrote:
So an hour or two of idling does no real harm? Often I just go down in the winter if I havent run the engines for a week or so and just run it in idle to warm up the boat and help keep it dry
I don't think the way you're doing it is particulary good for the engines.* We do the same thing--- run the engines if my schedule and the winds keep us from talking the boat out for four weeks in a row.* But we don't just let the engines idle.* We put them in gear and run them up to about 1300 rpm after a normal warm-up period at idle.*This puts a load on the engines and gets them up to the proper cylinder temperatures for complete combustion.* Once they are at temperature--- which takes about 15 minutes at 1300 rpm*after initial warm up--- we run them for another 20 minutes, still in gear,*and then shut them down.

We used to do this with one transmission*in forward and one in reverse to minimize the load on the dock cleats.* But after reading that the BW Velvet Drive transmission is not as strong in reverse as it is in forward we now do one engine at a time in forward.* Both engines together would put quite a strain on the lines and cleats.*
__________________

Marin is offline   Reply With Quote
Old 10-25-2011, 11:22 PM   #23
Senior Member
 
Jay N's Avatar
 
City: Edmonds, WA
Country: USA
Vessel Name: WESTERLY
Vessel Model: 1974 Pacific Trawler 37
Join Date: Oct 2007
Posts: 387
RE: A new and excellent post on underloading

Here is a excerpt from my operating log:

Cruising:* Find a smooth spot anywhere between 1500-2000 rpm.* Ideally, the coolant temperature should be no less than 180E F when cruising, the hotter the engine runs, the less carbon and varnish that will form at the injectors and valves, and the less the engine will smoke at idle.* If 15-1600 rpm for a long run is desired, consider initially running the engine at 1800 rpm for 10 minutes or so to get cylinder temps up first. [The engine typically does not load up after a long run at 1600 rpm, but may smoke a little the next time you start it.* Cummins advises that:ALight load operation (less than 30% load) for extended periods (more than 8 hours) should be followed, whenever possible, by at least 30 minutes of high-power operation to burn off fuel residue and reduce the chance of developing long-term engine problems. This high-power operation should be conducted at a minimum of 50% of prime power.@* While this guideline is meant to address lightly loaded fixed-speed engines (such as generators), Tony Athens (Boat Diesel moderator and Cummins mechanic) recommends that operation of variable speed propulsion engines be held to a similar standard, depending on application/installation.] *Based on experience with this engine in this application and typical usage at 1500-1800 rpm (15-26% load), the engine should be operated at 2200 rpm (52% load) for 30 minutes every 25 hours of engine operation.

This scenario has been in place for a number of years, and engine performance has been very good.

*
Jay N is offline   Reply With Quote
Old 10-25-2011, 11:30 PM   #24
Senior Member
 
Jay N's Avatar
 
City: Edmonds, WA
Country: USA
Vessel Name: WESTERLY
Vessel Model: 1974 Pacific Trawler 37
Join Date: Oct 2007
Posts: 387
RE: A new and excellent post on underloading

Regarding operating equipment in the off-season, if I can't take the boat out and run everything for a couple of hours every 3-4 weeks, the boat will sit, although I will try to operate non-engine systems every 30 days.

Only twice in the past 14 years has the boat been laid up for 3-4 months in a row, and the engine is*then pre-lubed*prior to starting.
Jay N is offline   Reply With Quote
Old 10-26-2011, 07:36 AM   #25
Guru
 
Edelweiss's Avatar
 
City: PNW
Country: USA
Vessel Model: 1976 Californian Tricabin LRC
Join Date: May 2011
Posts: 1,834
RE: A new and excellent post on underloading

Quote:
Marin wrote:We used to do this with one transmission*in forward and one in reverse to minimize the load on the dock cleats.* But after reading that the BW Velvet Drive transmission is not as strong in reverse as it is in forward we now do one engine at a time in forward.* Both engines together would put quite a strain on the lines and cleats.*
*I can't speak for your boat manufacture or the model of Velvet Drive you have, but as an example most Californians, since the 1970's have Borg Warner Velvet Drives and don't use counter rotating engines, one transmission runs in reverse and one in forward. *Unless you have one counter rotating engine, one transmission is always running in reverse, when going ahead, otherwise you wont have counter rotating propellers.*
*
You might want to note your Velvet Drive model and serial number and check that information with a reputable marine transmission shop.
Edelweiss is offline   Reply With Quote
Old 10-27-2011, 05:05 AM   #26
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,533
RE: A new and excellent post on underloading

Both engines together would put quite a strain on the lines and cleats.

And might wash out the existing pilings at a high rate. One engine will wash out the bottom a bit slower.

It also will deepen the water under the props , so can only be used where the bottom wash will not shallow a channel
, or slips in the area.
FF is online now   Reply With Quote
Old 10-27-2011, 10:06 AM   #27
Guru
 
timjet's Avatar
 
Join Date: Apr 2009
Posts: 1,905
A new and excellent post on underloading

Quote:
superdiver wrote:
So an hour or two of idling does no real harm? Often I just go down in the winter if I havent run the engines for a week or so and just run it in idle to warm up the boat and help keep it dry (I have no power at my marina so I cant run a heater all the time). Is this doing harm to the engines?
*I don't think this is a good idea either.*

From personal experience the PO did this for about 2 years without bringing the engines up to normal operating temps. When I purchased the boat the PO ended up having to replace the injector pump timing gear, fuel cooler, S/O solenoid, and several other items I've since forgotten. I can't say any of this was due to his mis-conception that simply starting the engines once a month for 15 minutes or so was sufficient. However I've read from enough sources and from Tony on boatdiesel.com that the proper way to maintain your unused boat is to bring the engines up to operating temps and that will probably be more than letting them idle for 15 minutes. Operating temp for my engines is 180 deg, but they will only achieve 140 if left to idle for a half hour or so.*

I cruise single engine frequently with the operating engine at 1200 rpm. Once the temps get to 180 they seem to stay there even if left at the lower rpm's. I do however run the engines up to cruise rpm (2200) for 10 minutes at the end of the day if I've been cruising at lower rpms for any length of time.*

You mentioned that Tony has never seen a diesel engine destroyed by underloading but overloading is a real killer. I've taken an 1" out of my props because I heeded that advise.

I hope I'm doin the right thing, I'm no mehanical engineer, but I think I'm relying on the advise of those who are. *


-- Edited by timjet on Thursday 27th of October 2011 10:12:48 AM
timjet is offline   Reply With Quote
Old 10-27-2011, 09:19 PM   #28
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
A new and excellent post on underloading

Quote:
Edelweiss wrote:Unless you have one counter rotating engine, one transmission is always running in reverse, when going ahead, otherwise you wont have counter rotating propellers.*
There is no such thing as a counter-rotating Ford Lehman 120 (at least I've never heard of one).* All FL120s turn counter-clockwise when viewed from the rear.

We have counter-rotating propellers on our boat as*do all twin-engine Grand Banks,*but both our Velvet Drives run in forward when the boat goes forward and they both turn the same direction, counter-clockwise just like the engines.* The opposite (clockwise when viewed from the rear)*rotation of the starboard output shaft is achieved by an additional gear in the*output drive of the starboard transmission.* This is why the gear ratio between a "counter-clockwise" Velvet Drive is slightly different from the gear ratio of a "clockwise" Velvet Drive.* The ratios are 2.1 to 1 (port, counter-clockwise turning output shaft), and 1.91 to 1 (starboard, clockwise turning output shaft).* The 1.91 to 1 transmission is the one with the additional gear.

(As a point of interest, single engine GBs from the Velvet Drive era use the 2.1 to 1 version of the transmission, the one without the additional gear.)

I have never heard of a Velvet Drive actually being run in reverse to achieve opposite rotation from the engine, but some may do this I suppose.* All the "counter-rotating" Velvet Drives I've heard about in other boats and on the Grand Banks owners forum have the additional gear in the output drive.* Regardless of which way the output shaft turns, the main part of the transmission always turns the same way as the engine and the transmissions are always in forward (when the boat goes forward).

The Velvet Drives I'm familiar with have more drive plates for forward than reverse.* In fact, I think there's only one for reverse, but I could be mistaken.* This is why I've been cautioned not to run our transmissions hard in reverse.


-- Edited by Marin on Thursday 27th of October 2011 09:26:32 PM
Marin is offline   Reply With Quote
Old 10-31-2011, 08:01 PM   #29
JAT
Guru
 
JAT's Avatar
 
Country: US
Vessel Name: Just a Tinch
Vessel Model: Gulfstar 44 MC
Join Date: Jan 2010
Posts: 595
RE: A new and excellent post on underloading

Quote:
Steve wrote:
I wonder how common noticable damage from idleing or underloading diesel engines is, and at how many hours has it occurred? I have never heard of one damaged by it although they may be out there. Are any statistics available?
Steve W.
*

I think you will find that idling a diesel for extended periods really isn't too much of an issue. *Underloading isn't that much of an issue either.

My 2007 Cummins ISM that is in a semi-tractor has 425,000 miles on it, and of the 13,000 + hours on it...probably 3000 hours are at idle speed with or without a PTO engaged. * *

I think too many people worry too much about too much when all they should worry about is that the engine is running well and efficiently.

*
JAT is offline   Reply With Quote
Old 10-31-2011, 08:23 PM   #30
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,722
RE: A new and excellent post on underloading

Being an old truck driver I can attest to the fact that there is a lot of time on truck engines that are underloaded or even at idle but on the road there are hills most everywhere, stoplights, stop signs, slow drivers, turns and curves that slow the truck down or stop it. Once stopped the truck engine gets to go through 10 gears or so *to get the truck back up to speed * ....pedal to the metal in all gears. And even in Kansas running down the straight and almost flat road the truck will probably work harder that a typical trawler. Just rolling 18 really big tires and wheels take quite a bit of power. Truck engines work hard even though they have lots of low load and idle time. So the idea that trucks are underloading is just incorrect. So I agree w JAT. As long as the engine dos'nt idle (or nearly so) there should'nt be much to worry about. But still I think it's better for a diesel to work fairly hard.
Nomad Willy is offline   Reply With Quote
Old 10-31-2011, 09:18 PM   #31
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: A new and excellent post on underloading

Trawler speeds are easy.
Attached Thumbnails
Click image for larger version

Name:	whata wake.jpg
Views:	44
Size:	69.2 KB
ID:	8217  
markpierce is offline   Reply With Quote
Old 10-31-2011, 09:43 PM   #32
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: A new and excellent post on underloading

Quote:
nomadwilly wrote:
Once stopped the truck engine gets to go through 10 gears or so *to get the truck back up to speed * ....pedal to the metal in all gears. And even in Kansas running down the straight and almost flat road the truck will probably work harder that a typical trawler. Just rolling 18 really big tires and wheels take quite a bit of power. Truck engines work hard even though they have lots of low load and idle time.
*What Eric describes is why the Ford of England Dorset diesel (the engine marinized by Lehman into the Ford Lehman 120) was such a dismal failure in it's designed purpose, to be*a truck engine.* The high loads, constant rpm changes, lugging, and high revs typical of truck service were hell on the engine, and it just couldn't take it.* I was told by a retired British fellow we met whose company specialized in servicing, repairing, and overhauling diesel engines in England that the Ford Dorset suffered all sorts of problems when it was put into a truck.* The injection pumps in particular, he said, were very high maintenance items.

It wasn't until the engine was tried in a stationary, constant-load, relatively constant rpm industrical application that it showed promise.* Which is why its use in trucks was very short lived but it's use in cranes, generators, pumps, tractors, and harvesters--- and boats--- was pretty successful.
__________________

Marin is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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
Recommendation for MarinePro - Excellent service in Mid-Atlantic area Gull General Discussion 0 03-24-2011 02:43 PM
First post, and yet another "what boat" post syf350 General Discussion 49 09-20-2010 04:12 AM
First post GlennW General Discussion 4 07-18-2010 05:05 PM
HOW TO--(Post an Avatar) BOB CRISMON How To Use The Forum, Site News & Account Concerns 4 10-12-2007 11:09 PM




All times are GMT -5. The time now is 07:05 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012