Reply
 
Thread Tools Display Modes
 
Old 02-25-2014, 06:14 PM   #1
Veteran Member
 
City: Bayfield, WI
Country: USA
Join Date: Jan 2013
Posts: 92
Diesel wear and tear

Every day I get closer and closer to severing my ties with 64 years of sailing. Well, the boat hasn't sold yet, but, getting closer.
Anyway, after all these years of boating you would think that I would have some informed opinions about engines in general even if the largest diesel I have ever owned is 35hp.
As we look at "trawlers" in general (forget about displacement or semi-displacement) there are single and twin engine. Ok, but, all the twins seem to be over powered for the size boats. We love traveling at 5-7 kts. We can run our 35hp diesel at 3/4 throttle and use maybe a little over 1/2 gallon an hour. We have been told that if we run large diesels at low rpm's we will ruin them in short order. If that is true, how many engines are ruined by doing the "loop?" There aren't many places where you can run up over 10kts.
At our age we want more creature comforts afforded by a trawler. However, we aren't exactly thrilled about feeding $20,000 worth of diesel through one just to do the loop.
__________________
Advertisement

Barpilot is offline   Reply With Quote
Old 02-25-2014, 06:33 PM   #2
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
kinda depends on the diesel...Lehmans are notorious for lasting despite continuous low RPM cruising.

The debate I have always heard and find comes full circle...is many diesels once broken in can run all day at lower RPMs and not suffer greatly. Some manuals will give guidance as to when and how long they should be run at higher RPM to overcome a day run at low RPMs.

Some engines have a history of doing well at low RPMs...others not so.

But to arbitrarily say running a diesel at less than 80-90% load is automatically bad is just uninformed.
__________________

psneeld is online now   Reply With Quote
Old 02-25-2014, 06:47 PM   #3
Dauntless Award
 
Wxx3's Avatar
 
City: New York, NY
Country: USA
Vessel Name: Dauntless
Vessel Model: Kadey Krogen 42 - 148
Join Date: Jan 2013
Posts: 2,313
Welcome to my world.

Also, totally agree with Psneeld.

So, for a 42 foot boat, you probably need about 65 hp to go 6 to 7 knots, a little more hp for high winds.

Having said that, I love my Sp 135

I get 1.5 gal/hr at 7 knots and if I cut back to 1500 rpm and aobut 6 kntos, will consume 1.1 gal/hr

It purrs like a kitten and puts me to bed every time
__________________
M/Y Dauntless, New York
a Kadey Krogen 42 Currently https://share.delorme.com/dauntless
Blog: https://dauntlessatsea.com
Find us: https://share.delorme.com/dauntless
Wxx3 is offline   Reply With Quote
Old 02-25-2014, 07:04 PM   #4
Guru
 
SCOTTEDAVIS's Avatar
 
City: Vero Beach, FL.
Country: US
Vessel Name: FIREFLY
Vessel Model: Pilgrim 40
Join Date: Nov 2012
Posts: 913
Put a bit of a load (50-70%) on a diesel and it's happy, don't let it overheat by paying attention to the cooling system.

High HP engines generally have a forced induction system (turbo/super charged) and they need to work harder to get under a load because they make more power to begin with.

Normally aspirated engines in the 75 to 130 HP range will power a trawler very happily running in the 1400-1800 RPM range for darn near ever.

Don't run a fast boat slow all the time and don't run a slow boat on the pins all the time.

Most boats are overpowered for the use they get.
SCOTTEDAVIS is offline   Reply With Quote
Old 02-25-2014, 08:13 PM   #5
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,820
If you want maximum efficiency out of a modern diesel, ideally you want to run it at or above the rpm that delivers peak torque. If you want to have it last a long time you need to burn enough fuel at that rpm to maintain proper operating temperature. Unfortunately most boats aren't setup to run 7 knots or less within those parameters.

With fuel at $4 a gallon and only likely to go up, repowering the vessel of your choice with either new or a remanufactured engine to obtain efficient operating paramenters makes all kinds of sence ...... or dollars.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-25-2014, 08:25 PM   #6
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,889
Generally no harm in running even high output diesels at low load settings. I make my living with these engines and have never seen a failure from someone running hull speed.

Lots of talk on "them thar interwebs" about how you have to run a diesel at 75% load or whatever to last. Nonsense. Show me an engine that has failed due to running at 20%. Have not seen one.

It is true that the engines will "load up" with unburnt fuel/lube, but this can be handled by a daily hard run for a couple minutes. But even one boat that basically idled all the way from NC to Key West and back- engine had no apparent problems. Blew a good cloud on power up, but cleared right up.

Running an engine harder than necessary for hull speed- you will burn way more fuel, and if the trip is long enough, enough fuel to pay for cylinder kits. Which you will likely not need.
Ski in NC is offline   Reply With Quote
Old 02-25-2014, 09:13 PM   #7
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 3,202
Quote:
Originally Posted by Ski in NC View Post
Generally no harm in running even high output diesels at low load settings. I make my living with these engines and have never seen a failure from someone running hull speed.

Lots of talk on "them thar interwebs" about how you have to run a diesel at 75% load or whatever to last. Nonsense. Show me an engine that has failed due to running at 20%. Have not seen one.

It is true that the engines will "load up" with unburnt fuel/lube, but this can be handled by a daily hard run for a couple minutes. But even one boat that basically idled all the way from NC to Key West and back- engine had no apparent problems. Blew a good cloud on power up, but cleared right up.

Running an engine harder than necessary for hull speed- you will burn way more fuel, and if the trip is long enough, enough fuel to pay for cylinder kits. Which you will likely not need.

Thank You! Just get in the boat and go.
__________________
www.MVTanglewood.com
twistedtree is online now   Reply With Quote
Old 02-25-2014, 11:12 PM   #8
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
Barpilot,
You are now (as a shopper) in the drivers seat. You have the power to find and purchase the boat that YOU think is right based on all the information you have at your disposal. Ask around and don't overlook engine manufacturers and engineers. If I had a 32 Nordic Tug and needed or wanted to burn 1.5 gph (or go 6.5 to 7 knots) I'd need to sell the boat or repower to do it if I found underloading unacceptable. You can avoid or minimize your exposure to being in that position before you buy a boat. After you buy you'll be stuck unless you find and buy a FD boat w a small engine .... 3 ton5hp per ton.

Having said that lots and lots of members have underloaded and overpropped boats for many years. Spend time in the archives as much opinion has been written over the years.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 02-26-2014, 05:49 AM   #9
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
Please send a photograph of the drive end of whichever engine interests you. I will look at it and let you know if it is efficient and suited for the purpose.
RickB is offline   Reply With Quote
Old 02-26-2014, 06:06 AM   #10
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,372
Quote:
Originally Posted by RickB View Post
Please send a photograph of the drive end of whichever engine interests you. I will look at it and let you know if it is efficient and suited for the purpose.
First off Rick, what color do you prefer?
sunchaser is offline   Reply With Quote
Old 02-26-2014, 06:21 AM   #11
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,534
There is little choice in engines purchasing a used boat , so the best that can be done is to purchase what has a good rep.

The Ford Econo power marinizations (Leman)seem to be popular with their owners , and as they were never heavy duty industrial engines , the design for a small truck or tractor works well at modest power.

How much service life is lost by underloading is moot on most small boats.

OK if you ran it to perfection it would go say 10,000 , BUT you underload it constantly , refuse to change the oil on installed time , just run time , and save by only changinf filters with every 3rd change.

So your 10,000 engine gets a half life,,,, 5,000 hours big deal.

5,000 hours is longer than many 40 year old boat engines have ever seen.

Dont worry , be happy,

And do proper maint and the engine will probably not require replacement while you own the boat.
__________________

FF 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





All times are GMT -5. The time now is 09:06 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