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Old 03-18-2016, 12:51 PM   #41
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Originally Posted by manyboats;
I'll get some more numbers to add to what I know and subtract from what I thought I know.
As confounding as I find it, I take comfort reading that comment coming from someone who has sniffed a lot more diesel than I.
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Old 03-18-2016, 02:34 PM   #42
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The question of the effect of low load running is a very interesting question for me, as the boat that I have an offer on has the Cummins QSB5.9L engine configured for 380hp. This is a single rail, turbocharged engine that Cummins classes as a "High Output" engine. I anticipate running this engine at about 30% hp or about 15% fuel burn. Nor sure what %load that would be.

From what I have been able to determine, this engine handles that very well with the caveat that oil temps are maintained high enough and that the engine is run for short periods at higher loading. However, I am relying on outside advice as I have no experience or knowledge.
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Old 03-18-2016, 02:43 PM   #43
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Mr. Steve D'Antonio laid out the ills from under loading , but not the internal cause.

Each firing cylinder must create enough pressure to get behind the compression rings and force them into proper contact with the cylinder walls.

Light load , the rings do not seal well and blowby contaminates the lube oil much faster.

The real hassle is the light ring contact burnishes (polishes) the cylinder wall.

This smooths the hone marks required to hold oil for the piston to slide on.

Compression is lost , and a later high load does ZERO to cure the problem , only new rings and a hone can restore the compression, and stop the slobbering.

A good heavy load may get rid of carbon buildup in the engine and long enough might free the stuck rings , but only an overhaul can repair the cylinder wall damage.

The trick is to load the engine at CRUISE RPM , heavy enough for the engine to be working hard , not loafing.

Best is a "just big enough " engine from the boat assembler , the choice in under 100HP is not large.

So over sized which is frequently cheaper is installed.

Power or sail this calls for a "cruise" prop , which will NOT reach max rated RPM .

But with the proper engine load at cruise frequently the over sized engine can be run slowly 1200-1600 RPM , nice and quiet.

An informed owner and an EGT gauge are required.
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Old 03-18-2016, 03:04 PM   #44
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For those not totally understanding how the "load" on your engine is defined I found a comment on an automotive forum that helped me to get a better grasp on just exactly what "load" means:

"The engine load is the torque output of the engine.

An internal combustion engine is - approximately - a constant torque motor, meaning it can produce the same maximum torque at any rpm. The fact that it happens at a rpm or another, dictates how much power it produces.

Torque is proportional to the amount of force put on the piston, which is proportional to the amount of air being burnt in the combustion chamber, which is why you can relate the engine load to the quantity of air going into the engine, knowing the maximum amount of air that go in at a particular rpm, i.e. at WOT.

RPM does not really depends on throttle opening per say. When an engine is at constant speed, there is only the friction force going against the engine (from the bearings) and some others to run pumps and such, such that the engine can run. This represents the load at idle.

If you give enough heat (fuel combusted) to produce enough torque to go against this load, the engine will idle at constant speed.

If you give more heat, it will produce extra torque which will be transformed into acceleration of the moving parts (F=ma or T=Iα in rotation). Of course, if you give less heat, there will be a deceleration of the rotating components.

But you can increase the load by coupling an external torque to the shaft of the engine (a pump for example or a vehicle that needs to be accelerated). In that case, if you don't increase the heat in the combustion chamber, the engine will begin to decelerate. But if you increase it enough such that the torque converted by the engine equals the torque required by the load, then the speed of the engine will stay constant."
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Old 03-18-2016, 03:23 PM   #45
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If we all understood the content of the last 10 posts we would never need to bring this up again.

HaHa ,
Less than a minute I see there's another thread on it.
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Old 03-18-2016, 03:23 PM   #46
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Quote:
Originally Posted by Diesel Duck View Post
... The engine load is the torque output of the engine.

An internal combustion engine is - approximately - a constant torque motor, meaning it can produce the same maximum torque at any rpm. ...
Torque is proportional to the amount of force put on the piston, which is proportional to the amount of air being burnt in the combustion chamber, which is why you can relate the engine load to the quantity of air going into the engine, knowing the maximum amount of air that go in at a particular rpm, i.e. at WOT.

RPM does not really depends on throttle opening per say. ...
Can't reconcile that.

My JD 4045 doesn't have a throttle. Engine speed is controlled via a governor.

Max. torque is reached at 1400 RPM, at a 30 percent engine load.

Usual cruising speed is at 1800 RPM, a 42-percent load.

100-percent load is achieved at 2400 RPM.
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Old 03-18-2016, 05:16 PM   #47
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Lets see if it works:


There are some power and fuel consumption graphs and "prop curve" which I don't understand (page 3).

Sunchaser - what are the best and the worst characteristics of these engines in your experience? Is your boat a planning hull boat?
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Old 03-18-2016, 08:14 PM   #48
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I'm impressed,
Very nice engine.
I like the 5" stroke.
I see they list "typical fuel consumption" as 7gph. So on the average It seems they expect one to load the engine at a 7gph burn rate. Most trawlers are twins .... wonder how many here are burning 14gph while cruising? I wonder if Perkins suspects their engines will be loaded way less than that?
Sure is a nice engine. I've seen them and that blue is beautiful.

Janusz,
The full power curve is a sequence of dots connected of wot power outputs ... loaded to specific and various rpms. Like if you were going up a hill w a big truck with your foot all the way into it at specific rpm's less that the rated rpm. All the points on the curve are at wot. They are probably throttled to maximum output .. not max fuel ..... in other words not over fueled.
The prop curve is a simulated or imagined loat that would be typical of a certian type of boat. If it's a smooth and fair curve the curve was probably generated for a FD or/and a SD hull slower than those that are close to planing.
This is a curve that will allow you to fairly accurately predict your fuel burn at various rpm's and speeds. It is assuming you're propped to your rated rpm. 2500rpm in respect to the subject Perkins. If your boat is propped correctly you can look at this curve and see fairly accurately what your boat will burn at any rpm along the prop curve.
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Old 03-18-2016, 08:29 PM   #49
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The engine is not electronically controlled. No computers.

The boat is Ocean Alexander -OA - not Marine Trader.

The oil analysis was done by my surveyor-mechanic 2 days ago using a Surrey lab. The oil change was approx. 1,5 yrs ago by previous owner.

He kept all the receipts, manuals, bills, ship's log etc and the whole documentation which takes a whole shelf and weighs at least 20 lbs, I am sure. That was one of the compelling reasons I bought this boat.
I hate to get into a spitting contest with you but that does not seem to be an Ocean Alexander.

That is a Marine Trader.

What info do you have that says OA?

http://www.yachtworld.com/boats/1982...s#.VuydFfkrK70
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Old 03-18-2016, 10:40 PM   #50
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Originally Posted by menzies;
That is a Marine Trader. What info do you have that says OA?
I wondered about the profile and that is why I asked. Bridge, side supports and railings don't say OA but I'm not taking it as far as you though. Interior doesn't look like Marine Trader either. But that was an era of great mystery in Taiwan.


Yacht World calls it an Ocean Alex, listing broker just says Ocean and it sure isn't one of those.

OA...
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Old 03-18-2016, 10:42 PM   #51
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Sunchaser - what are the best and the worst characteristics of these engines in your experience? Is your boat a planning hull boat?
I am not aware of any negatives. PS has been marinizing their newer design engines for their brand and Cat for about 15 years. Cat ownership helps to insure parts will be available for a very long time. The engines are built for industrial use for tractors, gensets, fork lifts etc.

My vessel is not a planing boat. At a normal cruise RPM of about 1750 fuel burn for both engines is a bit less than 5 gph including genset use. At 1600 RPM fuel burn drops by about 20%. PM me if you want more details.
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Old 03-19-2016, 01:04 AM   #52
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Smile

[QUOTE=menzies;425178]I hate to get into a spitting contest with you but that does not seem to be an Ocean Alexander.

That is a Marine Trader.

What info do you have that says OA?


- The boat is listed at Yachtworld as OA;

- My Bill of Sale calls it OA

- All the receipts and documents call it OA, back all the way to 1983;

- Two current and one 2013 survey call it OA

- My initial post shows the picture I have taken myself. There is an "Ocean Alexander" plate on top of first strut visible (you have to zoom in to read).

- On the dash at lower helm there is plate "Ocean 40";

- I have the copy of current Certificate of Registry issued by Transport Canada which in the box "Builder's name and place of build" says:
OCEAN ALEXANDER
KAOHSIUNG, TAIWAN

But, if you still prefer to call it Marine Trader that is fine; I have no problem with that. Whatever it is called its quality, beauty and functionality will remain unchanged.
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Old 03-19-2016, 01:12 AM   #53
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I wondered about the profile and that is why I asked. Bridge, side supports and railings don't say OA but I'm not taking it as far as you though. Interior doesn't look like Marine Trader either. But that was an era of great mystery in Taiwan.


Yacht World calls it an Ocean Alex, listing broker just says Ocean and it sure isn't one of those.

OA...


Yacht World calls my boat Ocean Alexander, and

The listing broker always said Ocean Alexander as I recall. He is vacationing now in Honduras (with my money).


The picture you attached is OA Europa built from 1983 on. It was always twin engine.
My boat is 1982 OA Europa designed by Ed Monk. Single screw, different hull profile.
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Old 03-19-2016, 02:12 AM   #54
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I hate to get into a spitting contest with you but that does not seem to be an Ocean Alexander.

That is a Marine Trader.

What info do you have that says OA?

1982 Marine Trader Europa Power Boat For Sale - www.yachtworld.com
I thought the same thing. In addition to the 3 deck supports it is the first OA 40 Europa I have seen with 3 front windows. I did some searching and found this 1977 OA 40 Europa that looks just like the OP's boat.

http://www.yachtsinternational.us/en...y.php?id=11949

I guess OA must have made some changes to the design in the early to mid 80's.

Nice boat BTW and congrats on the purchase!
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Old 03-19-2016, 06:31 AM   #55
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Janusz, As usual they sent you nothing bit advertising nonsense.

Ask for a FUEL MAP and see how responsive they are.

The fuel map, should they actually send one, will allow the easy setup of the vessel for economical cruising.

What they sent , a theoretical prop curve is fine if you are setting up to water ski.
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Old 03-19-2016, 09:55 AM   #56
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Originally Posted by Janusz;
But, if you still prefer to call it Marine Trader that is fine; I have no problem with that. Whatever it is called its quality, beauty and functionality will remain unchanged.
Enjoy your new hobby.
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Old 03-19-2016, 11:17 AM   #57
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Some corrections to comments above:


The only curve relevant to a boat is the prop curve. Props load engines and fuel is determined by load. A loaded diesel runs at the rpm allowed by the amount of fuel to produce the torque to spin the load. Add more fuel and the engine rpm increases because it can create more torque. An unloaded diesel at any rpm uses little fuel and produced only the torque to overcome losses.


max torque is measured at full load. The makers curve does not provide any clue as to where max torque may be at less than full load as set up in a boat.


Diesels are unthrottled. Only gas engines control air flow. diesels are fuel controlled.


You can't run an engine at some different percent of fuel and load. Load and fuel percent will necessarily be equal. see the prop curve as above.
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Old 03-19-2016, 11:39 AM   #58
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Some corrections to comments above:


The only curve relevant to a boat is the prop curve. Props load engines and fuel is determined by load. A loaded diesel runs at the rpm allowed by the amount of fuel to produce the torque to spin the load. Add more fuel and the engine rpm increases because it can create more torque. An unloaded diesel at any rpm uses little fuel and produced only the torque to overcome losses.


max torque is measured at full load. The makers curve does not provide any clue as to where max torque may be at less than full load as set up in a boat.


Diesels are unthrottled. Only gas engines control air flow. diesels are fuel controlled.


You can't run an engine at some different percent of fuel and load. Load and fuel percent will necessarily be equal. see the prop curve as above.
Tony Athens wrote a piece on this and I just looked for it and can't find it. THe title of it was something like "Props push boats....not engines".
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Old 03-19-2016, 12:01 PM   #59
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Tony Athens wrote a piece on this and I just looked for it and can't find it. THe title of it was something like "Props push boats....not engines".
Propellers Move Boats, Engines Just Turn Them - Seaboard Marine
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Old 03-19-2016, 01:19 PM   #60
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Long article, I'll have to get back to it but was just wondering what the story is with the 3 & 4 blades on the picture boat.
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