Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 22-12-2008, 04:18   #16
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,577
Images: 240
Quote:
Originally Posted by Capct
... So when Pascoe says 1500 hrs he is pretty close to being right ...
David Pascoe was not discussing Sailboat Diesel engines, which typically have very low rated power to displacement ratios.

Ie:
A 38.81 Cubic Inch Displacement Yanmar 2GM20 Diesel is rated 16 H.P. @ 3,400 RPM Continuous; which is only 0.41 HP/CID.
A 58.2 CID Yanmar 3GM30 Diesel is rated 24.1 H.P. cont.; which is only 0.41 HP/CID.
Even their 1 Hour “emergency” ratings (18.2 HP & 27.3 HP respectively) at 3,600 RPM are less than ˝ HP/CID.


Pascoe says:
“... I raised a lot of flack from my previous article in which I stated that the AVERAGE diesel runs about 1000 -1100 hours before overhaul. I stick by that number, but you have to understand that the AVERAGE includes high performance diesels, as well as those folks who do not maintain their engines at all; the ones who run them until they stop.

High performance diesels cause a tremendous drop the average since the go fast diesels often go bang at 600 hours or less...


... Diesel engines are capable of having a long life when the power to displacement ratio is low. But when they start jacking up the power, beyond what the manufacturer originally intended, that benefit disappears. There is a very simple formula you can apply to estimate service life: simply multiply the cubic inch displacement of the engine times one*. The result is the maximum amount of horse power you can have and still expect a reasonable service life. A 6V92 engine is 552 CID; at powers greater than 550, these engines don't last. At 450, they'll go 10 - 15 years easily..."

* Recommended CID / HP Ratio = 1
One or Less Horsepower per Cubic Inch Displacement is better, more is worse.

For David Pascoe’s complete “Gas vs Diesel” article, Goto:
Power Options: Gas -vs- Diesel Part II - by David Pascoe, Marine Surveyor on Marine Engines
__________________

__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 22-12-2008, 21:09   #17
Registered User

Join Date: Nov 2008
Posts: 12
Quote:
Originally Posted by GordMay View Post
High performance diesels cause a tremendous drop the average since the go fast diesels often go bang at 600 hours or less...
This is like saying how long is a piece of string, or how short in this case.

How can you include in such assessment modified engines? Modified engines should not be taken into account at all. If you ask how much is your truck engine going to last are you told in your answer to consider drag racing engines that blow up after a few seconds because they get thousands of HP out of them? Nonsense.

Any decent unmodified diesel engine not considering the Chinese disposable engines sold on e=bay will last a lot longer than 1500 hours before needing overhaul, a lot more than 5000 hours, and if properly looked after well over 10,000.
And in this answer no one considers performance enhanced engines, nor engines that don't ever get an oil change or that run out of oil or engines in boat that sunk. Those don't count, they fall outside the Gauss Bell.
__________________

__________________
Marc1 is offline   Reply With Quote
Old 23-12-2008, 04:52   #18
Registered User
 
bastonjock's Avatar

Join Date: Nov 2008
Location: Lincolnshire UK
Boat: Mac 26x
Posts: 169
i have a lot of people from the Perkins engine factory coming in to my workshop,the factory is 30 yards away from my unit.

I hear stories of 40 year old engines that are still in use,these days the Perkins engine is badged as a Volvo.

Over here in the UK the boating market is geared up for diesels,trying to find a marina that sells gas is nearly impossible,also diesel fuel is cheaper than gas,Diesel at the garage forecourt costs 1.00 per liter rsed diesel can be bought for 0.60 a liter.

My buddies prout sirrocco uses about 1 liter per hour at 5knots using a 15 year old diesel,the equivalent gas engine on a sirrocco a 9.9 yam burns 2 liters of gas per hour to do the same speed,so its either 0.60 an hour or 1.90 an hour,you can save your mooring fees if you run on diesel.

gas is just not practicle here in the UK,its hard to get a hold of on the coast and costs 3 times as much to use.

my next boat will be a diesel even if its 10 ft long
__________________
bastonjock is offline   Reply With Quote
Old 23-12-2008, 04:55   #19
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,577
Images: 240
I was not defending David Pascoe’s opinion, merely explaining my understanding of it.
It should be understood that Pascoe is a Power-Boat specialist, concentrating on go-fast planing boats. It’s common for these boats to have factory engines with very high power to displacement ratios, and turbo’s.
These engines do not equate to the typical sailboat auxiliary.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 23-12-2008, 05:21   #20
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 2,593
Pascoe is still wrong

My survey practice is about 50/50 sail vs power and I find that diesels in trawlers and motor yachts average about 10000hrs and sailboats about 5000hrs. I have come to believe that the saliboat engine has a shorter lifespan due to the way it is used and not through any fault of the engine.

Up here on Lake Ontario, Wednesday night racing is where most sailboats get used. They fire her up, driver her out of the harbour under full power, shut her down five minutes later then sail for a couple of hours and repeat the procedure on the way in. If driven properly (warm up & cool down) and maintained well there is no reason they should not last a lot longer, sail or power.

There is a tremendous amount of good information on Pascoe's site but there are a few nuggets better left outdoors.

Dirt people scare me.
__________________
boatpoker is offline   Reply With Quote
Old 23-12-2008, 06:08   #21
Registered User
 
stevensc's Avatar

Join Date: Nov 2007
Location: Thibodaux, Louisiana
Boat: Monk 36 Trawler
Posts: 679
"Pascoe says 1500 hours is all you can hope for between overhauls."
Ridiculous! An overhaul is expensive, if this were so how many boats would be built with diesel engines? Walk around a few docks, ask some owners questions. Better yet look at this site, www.boatdiesel.com
You can read posts there for nothing if you want toask a question on line you will have to register $25.00 per year if you have doubts about diesel engines it would be a good investment.
Back to diesel overhauls I would say the 5k-10k hours mentioned in two previous posts are much more realistic, for a reasonably operated, sized, and maintained diesel boat engine.
here is another opinion
"Diesel engines are built to finer tolerances than are gasoline engines. They will accept much more abuse and often deliver, if well maintained, 8,000 hours of hard work before need a major overhaul.
Good luck!
Steve
__________________
stevensc is offline   Reply With Quote
Old 23-12-2008, 06:33   #22
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,577
Images: 240
Quote:
Originally Posted by boatpoker View Post
... I find that diesels in trawlers and motor yachts average about 10000hrs and sailboats about 5000hrs. I have come to believe that the sailboat engine has a shorter lifespan due to the way it is used and not through any fault of the engine.

Up here on Lake Ontario, Wednesday night racing is where most sailboats get used. They fire her up, driver her out of the harbour under full power, shut her down five minutes later then sail for a couple of hours and repeat the procedure on the way in. If driven properly (warm up & cool down) and maintained well there is no reason they should not last a lot longer, sail or power...

Dirt people scare me.
Welcome aboard, boatpoker.

As a professional Surveyor, you will have the opportunity to examine a larger number of different boats than most of us. Do you often have the opportunity to question selling owners about their standard operating procedures? If so, does their typical usage correspond to the condition of their engines?

I agree that no machinery can live up to it’s potential, when abused (the “typical” engine usage you describe, is abuse, IMHO).

What do you consider a “proper” warm-up, and what a proper cool-down?

It seems to me, that once the oil pressure is fully up, and the engine lubricated, a diesel engine should be good to go.

I also wonder how one cools down an engine. A functioning thermostat will keep the engine at it’s designed operating temperature, until you shut it down; at which time there will be a rapid, but short-lived temperature rise.

Thanks for your (professionally & personally) expert contributions.

As a C.L.O.D., should I take offense at your closing comment?
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 23-12-2008, 07:38   #23
Sponsoring Vendor
 
Tellie's Avatar

Community Sponsor

Join Date: Oct 2007
Location: Hollywood, Fl.
Boat: FP Athena 38' Poerava
Posts: 3,046
If someone is only getting 1500 hrs out of a diesel before rebuild, chances are high it's because of the way the engine is treated or neglected. Chances are the same owner is going to treat a gas engine the same way. My bet would be a gas engine treated the same way wouldn't even hit the 1500 hr mark under the same conditions.
Tellie is offline   Reply With Quote
Old 23-12-2008, 15:13   #24
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 2,593
Gord: No offense intended. We all fear what we don't understand. A diesel should never be idled for more than a few minutes. Start the boat, give it a couple of minutes to ensure it will stay running, cast off and slowly bring the throttle up (This may take 5 or even 10 minutes depending on size of engine) unitl it reaches full operating temperature, then you can pretty much run it as hard as you like. When coming back to dock the reverse applies. When you are about a half mile from home start bringing the throttle down until the engine hits about 160 degrees F. At this temperature you are ready to turn her off.

Diesels will take tremendous abuse if allowed to warm up and cool down properly as they operate at much higher temperatures than gas engines and all those metals cool and expand at different rates.
__________________
boatpoker is offline   Reply With Quote
Old 23-11-2009, 02:06   #25
Registered User
 
boris's Avatar

Join Date: Sep 2007
Boat: warwick 44
Posts: 108
we normaly work on 1 litre per hr per 10 hp being used
__________________
boris is offline   Reply With Quote
Old 28-11-2009, 06:04   #26
Registered User

Join Date: Nov 2009
Location: Keene NH
Boat: Home built Devlin Surfscoter27
Posts: 6
Wow, lots of almost accurate info here. Diesels engines don't always produce more particulate! The older ones did but the newer generation of common rail engines produce almost no particulate. Diesel fuel has about 12% more energy in a gallon than gasoline and diesels are more efficient at burning the fuel which can result in an increase in efficiency over gasoline of as much as 25%. The amount of hours per year have little or no effect on the life of the engine. It has more to do with the way the engine is used. Finally you will find duty ratings for diesels, 1 - 5. This is related to how long they will last and how hard they can be run. It is not unusual to get 20,000 hours from an engine with a duty rating of 5.
__________________
FlyingDog is offline   Reply With Quote
Old 29-11-2009, 04:41   #27
Registered User
 
BillAU's Avatar

Join Date: Feb 2009
Location: Corio
Boat: Careel 22
Posts: 452
The secret of keeping a diesel happy is simply to keep the engin clean, do the oil changes when reccommended in the manual and replace the air and oil filters as required in the service manual. Also a good moisture/water filter/trap in-line between the fuel-tank and the engine fuel pump could save you a lot of headaches...specially in the tropics.
__________________
No-one knows but...You could be dead for a long time! So treat others as you would have them treat you! Go out in the world and enjoy your life
BillAU is offline   Reply With Quote
Old 04-12-2009, 15:25   #28
Registered User

Join Date: Dec 2009
Boat: Marlow Explorer 78'
Posts: 5
diesel,diesel,diesel ! its safer and far less volatile.
78-Quality time
__________________
78-Quality Time is offline   Reply With Quote
Old 09-10-2012, 15:12   #29
Registered User

Join Date: Nov 2011
Posts: 36
Re: Gas or Diesel on a 38-42' Cruiser?

I opted for an old perkins 135 diesel as I like the fact that when they are running it runs. Gas engines has a way of being more dependent on different electric stuff, and I feel it is harder to troubleshoot them if something goes wrong. My old naturally aspirated diesel is quite simple, but no speed beast. It purrs nicely in about 7 Kent's cruise speed at 2000 rpm and is happy as long as the oil and filters are changed every now and then.
__________________
lostviking is offline   Reply With Quote
Old 09-10-2012, 17:17   #30
Registered User
 
Greggegner's Avatar

Join Date: Nov 2010
Posts: 406
Quote:
Originally Posted by 78-Quality Time
diesel,diesel,diesel ! its safer and far less volatile.
78-Quality time
Yes diesel doesn't explode...
__________________

__________________
Greggegner is offline   Reply With Quote
Reply

Tags
diesel

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
Manta 42' Catamaran DAA Multihull Sailboats 54 23-10-2011 20:34
Bluewater Catamarans - 36-42' Seman Multihull Sailboats 8 25-06-2009 12:30
which is heavier gas or diesel? bmartinsen Engines and Propulsion Systems 8 25-02-2009 10:23
Marine Engine Course Diesel/Gas Chief Engineer Engines and Propulsion Systems 19 10-07-2008 16:35
Manta now the best value for a 42' cat schoonerdog Multihull Sailboats 49 14-02-2008 05:24



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:43.


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.