Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 23-12-2018, 12:03   #1
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
heavy displacement repower dilemma

I am in the process of "rebuilding a new boat" for long term cruising and long passages. One of the many hurdles is choosing the best option for repower.

Originally this 40 footer steel Pilot House tipped the scales at 42,000 pounds (loaded) and had a 130hp Mercedes OM352 with 2:1 and 23 inch screw. She burned roughly 7gph.

Hull is rated to 85hp (12m and 27000 lbs dry weight)

Here are my concerns

1. WEIGHT. the whole boat is undergoing major refit and mods to get her weight down closer to 30000 lbs. The Mercedes and box runs 1500 pounds. All the running gear is heavy to handle that kind of power.

2. HEIGHT of motor. The Mercedes is 32 inch tall. A lower motor will allow lowering floor in pilot house, allowing to lower pilot house roof, which makes windows smaller all adding benefits to the overall project requirements.

3. FUEL CONSUMPTION. Being it is a motor sailer, it will motor often and lower consumption means less fuel, less weight etc. I heard an argument made that more power allows you to use a smaller percentage of the motors capacity therefore using less fuel. I think using 80 hp of a 200 hp engine will use the same fuel as a 80 hp motor..

4.SIMPLICITY. This is the one that is really causing loss of sleep. I can McGiver a naturally aspirated diesel together in an emergency. The new common rail turbos could solve all these other concerns, but at the cost of simplicity. If the motor quit, I could be in trouble.

I would love to hear what folks who cruise long term with a heavy boat think about engine choice. Fuel concerns, weight concern, available parts around the globe, ability to service and repair, etc. etc.
Salmoneyes is offline   Reply With Quote
Old 23-12-2018, 22:13   #2
Registered User

Join Date: Oct 2009
Location: australia
Posts: 539
Re: heavy displacement repower dilemma

Perkins HT 6354. [Horizontal]
shakey doug is offline   Reply With Quote
Old 24-12-2018, 02:20   #3
Senior Cruiser

Cruisers Forum Supporter

Join Date: May 2013
Location: Oregon to Alaska
Boat: Wheeler Shipyard 83' ex USCG
Posts: 2,859
Re: heavy displacement repower dilemma

I have Detroit Diesels in an 83', 80 ton boat that burns about .85gl/mile @ 10kts. The engines are 100% mechanical, no electrical requirements at all. Rated HD commercial, continuous. Parts are world wide. Engines were designed to be rebuildable many times. In fact, everything on the engine is designed to be rebuilt in the field. My current mains are 70 years old.

If I was building a new boat, I'd find a good pair of Detroits and rebuild them to new. They aren't the most economic, but are the most reliable.
Lepke is offline   Reply With Quote
Old 24-12-2018, 06:14   #4
Registered User

Join Date: Jan 2009
Location: San Diego, California - Read about our circumnavigation at www.rutea.com
Boat: Contest 48
Posts: 995
Images: 1
Re: heavy displacement repower dilemma

We repowered our 48’, 40,000-pound ketch 10 years ago and just completed an 8-year, 48,000-mile circumnavigation where we put over 4,000 hours on the engine. Before we repowered, I had seriously considered both Volvo and Yanmar, however, rejected both as too light duty. I ultimately settled on a Beta Marine 90 as its block is built by Kubota and is designed for use in construction equipment. The engine and transmission weigh less than 800 pounds and it’s been virtually flawless in its operation. I had also wanted a naturally aspirated engine and one that uses a mechanical injection pump - both features of the Beta Marine 90. The support I received from the Beta Marine dealer in North Carolina was excellent but I never had to search for parts when we were in remote parts of the world.

I would never consider installing a Detroit Diesel - it has one of the worst weight-to-horsepower ratios of any engine out there. They’re noisy, inefficient, they tend to leak badly (called ‘seepage’ by the manufacturer as leaks are covered by warranty), they vibrate terribly and parts are expensive. Yes, they’re reliable but most modern engines are.

Fair winds and calm seas.
nhschneider is offline   Reply With Quote
Old 24-12-2018, 09:58   #5
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
Re: heavy displacement repower dilemma

Quote:
Originally Posted by Lepke View Post
I have Detroit Diesels in an 83', 80 ton boat that burns about .85gl/mile @ 10kts. The engines are 100% mechanical, no electrical requirements at all. Rated HD commercial, continuous. Parts are world wide. Engines were designed to be rebuildable many times. In fact, everything on the engine is designed to be rebuilt in the field. My current mains are 70 years old.

If I was building a new boat, I'd find a good pair of Detroits and rebuild them to new. They aren't the most economic, but are the most reliable.
Wow,, a ton per foot, and here I thought I was overweight, (no disrespect intended). I do have a little experience with the Detroits,, I drove a truck hauling cotton in 83 that had an 8V92, twin turbos and a super charger. Paid by the load. It was an ugly International and the truck rattled terribly, but boy was it fast. The best was that sound. No other big diesel makes that sound... I just looked and the little 4-53 are a dime a dozen, with an abundance of parts.

So you are recommending simplicity over efficiency... copy
Salmoneyes is offline   Reply With Quote
Old 24-12-2018, 10:06   #6
Registered User
 
Cheechako's Avatar

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 22,873
Re: heavy displacement repower dilemma

There's an old saying that goes something like this: "buy the lowest HP rated motor in the biggest block, not the highest Turbo HP in the smallest block "
I believe in that saying.
It amazes me your boat burns 7 GPH though. ? My 36k lb boat burned less than 1.5 gal per hour with an 80 hp Mercedes Diesel.
Mercedes parts are available in a lot of places. What really surprised me is the cost of actual Mercedes parts was cheaper by far than most marine engine parts. But my engine was based on the 240D engine which is probably the most widely built diesel ever made...
23" prop on a 40 ft boat? wow, that can be a great thing, but you need an old school slow turning diesel for it!
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 24-12-2018, 10:16   #7
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
Re: heavy displacement repower dilemma

Quote:
Originally Posted by nhschneider View Post
We repowered our 48’, 40,000-pound ketch 10 years ago and just completed an 8-year, 48,000-mile circumnavigation where we put over 4,000 hours on the engine. Before we repowered, I had seriously considered both Volvo and Yanmar, however, rejected both as too light duty. I ultimately settled on a Beta Marine 90 as its block is built by Kubota and is designed for use in construction equipment. The engine and transmission weigh less than 800 pounds and it’s been virtually flawless in its operation. I had also wanted a naturally aspirated engine and one that uses a mechanical injection pump - both features of the Beta Marine 90. The support I received from the Beta Marine dealer in North Carolina was excellent but I never had to search for parts when we were in remote parts of the world.

I would never consider installing a Detroit Diesel - it has one of the worst weight-to-horsepower ratios of any engine out there. They’re noisy, inefficient, they tend to leak badly (called ‘seepage’ by the manufacturer as leaks are covered by warranty), they vibrate terribly and parts are expensive. Yes, they’re reliable but most modern engines are.

Fair winds and calm seas.
Thank you. I too spoke with the Beta folks. Their recommendation was the Beta 85 -TM345. Power to weight is very good with this unit. After talking to a couple guys here, they told me about Kubota used for water pumps and generators that were 4 cylinder units, so after looking them up, I realized that the basic engine itself is fairly inexpensive. Beta adds all the marine gear which adds quite a bit of cost. I have not ruled anything in or out yet, but if I were to go Kubota, I think I would buy one, then marinize it with all my stuff. ( I strongly considering keel cooled anyway)..

I believe your plus one on simplicity then? over fuel efficiency from computer controlled common rail?
Salmoneyes is offline   Reply With Quote
Old 24-12-2018, 10:28   #8
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,969
Re: heavy displacement repower dilemma

I have a 15 ton, light-loaded steel pilothouse cutter (see picture to the left) and I expect to be 17 tons (34,000 pounds) fully loaded. I went from a 52 hp Westerbeke W-52 diesel to a Beta Marine 60 and upped my prop from an 18 x 13 three-blade fixed to a 19 x 15 four-blade Variprop feathering prop, the pitch of which I am going to flatten this winter in forward because I can't reach full revs, although good grief I can back down like a champ!

Given we appear to have similar boats (although you seem to have a lot more load than mean for some reason), I'm not sure why you require such a huge diesel. I hit hull speed in flat water at about 1900 RPM, which is why I'm actually flattening the prop to hit a better spot on the fuel map. Given that diesels run most economically at 75-80% of WOT, I would suggest you find one of the online HP/prop/boat size calculators to verify that you need that large an engine. I would suspect 75 HP would do you fine, of about 2.8L displacement over four cylinders. Better to work a smaller engine hard than to idle a bigger one, and your desire to have more room is easier to achieve.

But perhaps I'm missing something. In the meantime, you may enjoy the termination, so to speak, of my re-engining process.


https://alchemy2009.blogspot.com/201...terminals.html
__________________
Can't sleep? Read www.alchemy2009.blogspot.com for fast relief. Can't read? Avoid www.volumesofsalt.blogspot.com, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote
Old 24-12-2018, 10:30   #9
Registered User

Join Date: Oct 2015
Posts: 2,008
Re: heavy displacement repower dilemma

Quote:
Originally Posted by Salmoneyes View Post
3. FUEL CONSUMPTION. Being it is a motor sailer, it will motor often and lower consumption means less fuel, less weight etc. I heard an argument made that more power allows you to use a smaller percentage of the motors capacity therefore using less fuel. I think using 80 hp of a 200 hp engine will use the same fuel as a 80 hp motor..
This would be very BAD argument given by someone who does not know what they are talking about. Diesels like to run fully loaded, at what ever RPM they are running at. The problem is that a propeller power curve and a diesel power curve are very different, and can only match at one point, full throttle.

Spinning a propeller at anything less than full throttle, the engine is not fully loaded, and that is not good for the long term health of the engine, OR for its fuel efficiency.

Gasoline engines control speed by adjusting the amount of AIR that goes into the engine. The carburetor or fuel injection computer then adjust the amount of fuel to match, so the fuel to air ratio is always just about right no matter the load or speed. They are (more or less) happy to run at whatever combination of load and rpm you care to throw at them.

Diesels do not meter the air, only fuel. So when they are running lightly loaded they run a very lean mixture of fuel and air. The exhaust temperatures do not get as high as designed, and soot collects and fouls up things. Over time the soot hardens into "carbon" and you have a major overhaul on your hands.

The exception would be if you sprung for the extra dollars and added complexity for a real controlled variable pitch prop. These allow you to match the load to the RPM across a wide range of boat and engine speed. Fuel efficiency and engine life go up a LOT. For a heavy motor sailor like yours, this would be a great addition, but very expensive.

The proper maximum engine power rating is one that will drive the boat at, or a little above, theoretical hull speed at full rated RPM, and run the boat at cruising speed at close to the manufacturer's recommended maximum continuous duty RPM. Any other recommendation is dubious. Of course, you can always go smaller in engine size, but that has its own issues...
billknny is offline   Reply With Quote
Old 24-12-2018, 10:33   #10
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 8,841
Re: heavy displacement repower dilemma

Quote:
Originally Posted by Salmoneyes View Post
Wow,, a ton per foot, and here I thought I was overweight, (no disrespect intended). I do have a little experience with the Detroits,, I drove a truck hauling cotton in 83 that had an 8V92, twin turbos and a super charger. Paid by the load. It was an ugly International and the truck rattled terribly, but boy was it fast. The best was that sound. No other big diesel makes that sound... I just looked and the little 4-53 are a dime a dozen, with an abundance of parts.

So you are recommending simplicity over efficiency... copy
A 4-53 was my thought also. No bells and whistles to go wrong and is able to be run continuously.
Cadence is online now   Reply With Quote
Old 24-12-2018, 10:35   #11
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
Re: heavy displacement repower dilemma

Quote:
Originally Posted by Cheechako View Post
There's an old saying that goes something like this: "buy the lowest HP rated motor in the biggest block, not the highest Turbo HP in the smallest block "
I believe in that saying.
It amazes me your boat burns 7 GPH though. ? My 36k lb boat burned less than 1.5 gal per hour with an 80 hp Mercedes Diesel.
Mercedes parts are available in a lot of places. What really surprised me is the cost of actual Mercedes parts was cheaper by far than most marine engine parts. But my engine was based on the 240D engine which is probably the most widely built diesel ever made...
23" prop on a 40 ft boat? wow, that can be a great thing, but you need an old school slow turning diesel for it!
I was bummed about that fuel consumption as well. This is the motor they used for industrial stuff, then I guess it went into some uni mogs and other trucks.

She is just what you say, big box, small power. It could not be any simpler to work on, but I do not know how to improve its efficiency.

The guys that built her worked in a ship yard in Sweden that apparently built fishing boats, and used what was lying around. The shaft is a 9 foot 45mm unit that I can barely lift. Everything was built supper heavy duty which I guess is for safety in icy waters, but at the cost of efficiency. It sails very slow, so you motor a lot to get to that 7 knot range.

I was told that with the cooling system running under 150 degrees, this motor is no where close to its happy place and that alone may be the fix, but again, the weight.

I had a guy looking at it one day, and his idea was to utilize the huge hollow in the keel below the motor and set the motor as deep as possible then to remove some of the lead ballast in that area, which would help with the weight issue. Its an idea I keep going back to if for some reason the money runs out...
Salmoneyes is offline   Reply With Quote
Old 24-12-2018, 10:57   #12
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
Re: heavy displacement repower dilemma

Quote:
Originally Posted by billknny View Post
This would be very BAD argument given by someone who does not know what they are talking about. Diesels like to run fully loaded, at what ever RPM they are running at. The problem is that a propeller power curve and a diesel power curve are very different, and can only match at one point, full throttle.

Spinning a propeller at anything less than full throttle, the engine is not fully loaded, and that is not good for the long term health of the engine, OR for its fuel efficiency.

Gasoline engines control speed by adjusting the amount of AIR that goes into the engine. The carburetor or fuel injection computer then adjust the amount of fuel to match, so the fuel to air ratio is always just about right no matter the load or speed. They are (more or less) happy to run at whatever combination of load and rpm you care to throw at them.



Diesels do not meter the air, only fuel. So when they are running lightly loaded they run a very lean mixture of fuel and air. The exhaust temperatures do not get as high as designed, and soot collects and fouls up things. Over time the soot hardens into "carbon" and you have a major overhaul on your hands.

The exception would be if you sprung for the extra dollars and added complexity for a real controlled variable pitch prop. These allow you to match the load to the RPM across a wide range of boat and engine speed. Fuel efficiency and engine life go up a LOT. For a heavy motor sailor like yours, this would be a great addition, but very expensive.

The proper maximum engine power rating is one that will drive the boat at, or a little above, theoretical hull speed at full rated RPM, and run the boat at cruising speed at close to the manufacturer's recommended maximum continuous duty RPM. Any other recommendation is dubious. Of course, you can always go smaller in engine size, but that has its own issues...
I am in agreement here. I drive trucks once in a while, and in that world, there seems to be the argument that more horsepower is better for economy (assuming your foot is not connected to your ego) and having driven a wide range of trucks, there seems to be some proof to that. However, as you stated, water and pavement provide scenarios worlds apart.

I have spent a lot of time working on other folks boats, and I have seen first hand the soot build up from diesels not being run hard enough.

Your suggestion on the prop is a good one for us. Some folks we know use their main to supplement wind often, and that requires them to throttle back often. Kind of the fly in the ointment with heavy motor sailers really.
Salmoneyes is offline   Reply With Quote
Old 24-12-2018, 11:14   #13
Registered User
 
Russ's Avatar

Join Date: Jul 2008
Location: Satellite Beach, FL
Boat: Brewer 44' Steel
Posts: 245
Re: heavy displacement repower dilemma

Have 42' Ted Brewer Steel Pilothouse cutter. Came with 40 hp, PO upgraded to 60 hp. Cruised at 5 Kts barely at 0.9GPH.. That engine died and I upgraded to 110 hp Yanmar which drives the boat (55,000 lbs) at 8 knots for 2.3 GPH. Don't under power, it is a bear to not have the power to maneuver in a marina, against a headwind, etc. when ya need it.

Russ
__________________
Russ
Russ is offline   Reply With Quote
Old 24-12-2018, 11:14   #14
Registered User
 
Salmoneyes's Avatar

Join Date: Jun 2018
Location: Southern Oregon Coast
Boat: BR 12m Steel Pilot House Ketch
Posts: 51
Re: heavy displacement repower dilemma

Quote:
Originally Posted by S/V Alchemy View Post
I have a 15 ton, light-loaded steel pilothouse cutter (see picture to the left) and I expect to be 17 tons (34,000 pounds) fully loaded. I went from a 52 hp Westerbeke W-52 diesel to a Beta Marine 60 and upped my prop from an 18 x 13 three-blade fixed to a 19 x 15 four-blade Variprop feathering prop, the pitch of which I am going to flatten this winter in forward because I can't reach full revs, although good grief I can back down like a champ!

Given we appear to have similar boats (although you seem to have a lot more load than mean for some reason), I'm not sure why you require such a huge diesel. I hit hull speed in flat water at about 1900 RPM, which is why I'm actually flattening the prop to hit a better spot on the fuel map. Given that diesels run most economically at 75-80% of WOT, I would suggest you find one of the online HP/prop/boat size calculators to verify that you need that large an engine. I would suspect 75 HP would do you fine, of about 2.8L displacement over four cylinders. Better to work a smaller engine hard than to idle a bigger one, and your desire to have more room is easier to achieve.

But perhaps I'm missing something. In the meantime, you may enjoy the termination, so to speak, of my re-engining process.


https://alchemy2009.blogspot.com/201...terminals.html
Just went and looked at your blog.. We appear to think alike... I will take take the time to read the whole thing today...

My weight issues come from
1. 6mm steel hull deck down, rather than the 4mm in the plans
1a. but they followed the 7500# lead ballast all midship
2. 300 gallon water tanks
3. 400 gallons fuel
4. 1000 pound gen set
5. propulsion system double sized from plans

The boat is currently sitting naked with not a stitch of anything but steel. Our next plan is to take all the lines and start to produce a stability book. Then we can play with all the options for our mods. This is what has me chasing my tail since so many things rely on weights that are associated with decisions yet to be made. IE> the whole propulsion system, which its combined weight has to be factored in and properly placed.... Even that decision has to work around my craziest idea yet...Our tender, which I call a truck as opposed to the most common "taxi" we are all so familiar with... It is going to be heavy...
Salmoneyes is offline   Reply With Quote
Old 24-12-2018, 11:25   #15
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 8,841
Re: heavy displacement repower dilemma

As a suggestion. It the model has a T in it you don't want it.
Cadence is online now   Reply With Quote
Reply

Tags
displacement, men, repower

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Docking a Full Keel Heavy Displacement Sailboat Abrain Seamanship & Boat Handling 123 19-01-2016 12:41
Heavy Displacement Genoa In-Hauls zboss Monohull Sailboats 9 21-10-2014 16:28
Heavy vs Light Displacement andreavanduyn Monohull Sailboats 120 29-06-2013 02:30
For Sale or Trade: Heavy Displacement Anchor Rode thesparrow Classifieds Archive 4 30-03-2011 12:17
semi-displacement vs displacement samson General Sailing Forum 11 20-03-2011 13:05

Advertise Here


All times are GMT -7. The time now is 07:56.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.