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Old 03-15-2014, 12:12 PM   #21
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TT

Is the N60 fitted with the JD 6090 or JD 6081?
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Old 03-15-2014, 12:16 PM   #22
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TT

Is the N60 fitted with the JD 6090 or JD 6081?
The 6081 until about a year ago, at which point they switched to the 6090. I believe the 6081 was discontinued and replaced by the 6090 by Deere, but am not certain. What I do know is that the 6081 was being run at an M4 rating where the 6090 is M2 rated, so that's a distinct improvement.
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Old 03-15-2014, 12:41 PM   #23
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... The Nordhavn has a Deere 6090 M2 rated at 325hp. The M2 rating is full throttle for 16 out of 24 hours, and 100 RPM below that for the balance. So that's 2200 RPM for 16 out of 24hrs, and 2100 RPM for the rest. At 2100 RPM it's continuous rated.
Are we sure we're properly interpreting JD "M" ratings? My JD4045DFM70 is also rated "M2." So, full power operation is allowed 16 hours during a 24-hour period; however the stated load factor is equal to or less than 65% (actual fuel consumption divided by full-power fuel consumption). Sixty-five percent for my engine is about 2100 RPM out of a maximum of 2400 WOT. Thus, in my mind, anything between 2101 and 2400 RPM is "full throttle" limited to 16 out of 24 hours, a 299 RPM spread, not a mere 100 you cite for the Nordhavn's JD. (I usually operate at 1800 RPM, or a load factor of 43%)
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Old 03-15-2014, 02:13 PM   #24
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Are we sure we're properly interpreting JD "M" ratings? My JD4045DFM70 is also rated "M2." So, full power operation is allowed 16 hours during a 24-hour period; however the stated load factor is equal to or less than 65% (actual fuel consumption divided by full-power fuel consumption). Sixty-five percent for my engine is about 2100 RPM out of a maximum of 2400 WOT. Thus, in my mind, anything between 2101 and 2400 RPM is "full throttle" limited to 16 out of 24 hours, a 299 RPM spread, not a mere 100 you cite for the Nordhavn's JD. (I usually operate at 1800 RPM, or a load factor of 43%)
Well, I don't know. But looking at the specs more closely, and calculating out what 65% load factor would be, I think you are right. It's too bad the various vendors aren't clearer about this stuff.

First, I though I saw a note about cruise RPM being 100 less than max, but I must be mistaken about that. I do see a note saying it's 200 RPM less.

But reducing the engine RPM by 200 doesn't drop the fuel burn to 65% of full power, so now I'm really confused since I have two conflicting specs. Which do I follow?

If we assume (a bad thing) that we can't exceed either limit, then it means we can't run over 2000 RPM for more than 16/24 hrs AND we can't burn more than 65% of full power burn. That means when we are running below 2000, we need to get in a bunch of time well below 2000 to get the overall burn down. For reference, the 65% burn rate happens at about 1850 RPM, which suggests that's the continuous load point.

Now, just when I think I understand it, I look at the M1 continuous rating and it allows for 2100 RPM non-stop, 24x7, which is well over 65% of the M2 fuel burn. OK, so which is the real continuous rated RPM? 2100 or 1850?

So we have 3 seemingly conflicting specs.

But, like you said, it's really moot since nobody is likely to run that hard anyway. I sure won't, so I'm not going to worry about it too much.
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Old 03-15-2014, 02:25 PM   #25
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Now, just when I think I understand it, I look at the M1 continuous rating and it allows for 2100 RPM non-stop, 24x7, which is well over 65% of the M2 fuel burn. OK, so which is the real continuous rated RPM? 2100 or 1850?
My interpretation is "M1" means full power can be applied continuously, 24 hours a day.

http://www.deere.com/common/docs/pro...e_brochure.pdf
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Old 03-15-2014, 02:31 PM   #26
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My interpretation is "M1" means full power can be applied continuously, 24 hours a day.

http://www.deere.com/common/docs/pro...e_brochure.pdf
I agree. But why is that different from an M2 running 24x7 at 65% load factor? To get a 65% load factor on an M2, you need to drop the RPMs to 1850. Shouldn't it be 2100 just like M1?
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Old 03-15-2014, 06:54 PM   #27
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torque and egt

My boats been overpropped for all its 200,000 miles, with an average of 5.5mpg (including genset use) 25,000 hours on the last engine which was replaced by a JD 4045D/80hp due to lack of support/spares by MANN.

What I found is that the 16 hours out of 24 (m1-m2-m? stuff) is related to Exhaust Gas Temps, which for a dumb Deere is limited to about 1100 degrees-maintaining that 24/7 will burn exhaust valves( meaning loss of compression and the associated costs) EGTs=load.

The torque peak (the twisting/screwing force) on the Deere is 1200-1400rpm and it diminishes after that point-the HP goes up but the torque drops. All diesel engines develop max torque at lower rpm than max HP.

On a 40ft waterline, 40,000 pound boat I do 7.1 knots at 1200rpm-8.4 at 1400rpm. my EGTs are 500-650 degrees-running a 32/28 3 blade and 2.85 reduction-IF I ran a sub 28 inch prop I could hit my engines "redline" of 2400rpm- and be outside of the torque peak.My valves will never burn out-my water temps are 175-180. No smoke issues.

If you read your EGT-and operate your boat in the meat of your torque curve, not your HP curve, and adjust your injection pump timing, the degrees BTDC when it squirts you get it all, economy, power and longevity.

This is not rocket science-Engine manufactures want you to engineer your boat to their engine-for emissions.

or you can tune their engine to your boat.

That's my 2 cents-most will disagree
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Old 03-15-2014, 08:47 PM   #28
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Underpropped?

Thanks for all of the great responses to my post.
I have read thru them all numerous times to absorb the data. It's very possible that my prop is exactly what it should be

Looks like I need to do some accurate testing to come to a conclusion.
My engine is rated at 2500RPM, and I max out WOT at 2500RPM's with my current 25x16 prop. (Temps are 180 or less at full and I have calibrated my RPM gauges with a phototach)
Need to do a test and plot my speeds at 100-200 RPM increments and plot a curve.
Engine loading/exhaust temps appear to be an important factor that I need to determine also. It's clear that a higher load at a given RPM will increase temps, so what is the best way to determine what the engine loading is?

thank you,
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Old 03-15-2014, 08:58 PM   #29
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If your boat runs up to full rated RPM, which is does, then that's where your max load is. Every other operating point will be below the engine's allowed loads. Take a look at the load curve that I posted to see what I mean.

The long and sort of it is that if your EGT is OK at wide open throttle, you should be good at all other speeds.
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Old 03-15-2014, 09:36 PM   #30
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Jeff,

If you burn 4gph at WOT and 3gph at cruise you're at 75% load in cruise.

Check the manufacturers specs for WOT fuel burn.
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Old 03-16-2014, 07:51 AM   #31
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Jeff,

If you burn 4gph at WOT and 3gph at cruise you're at 75% load in cruise.

Check the manufacturers specs for WOT fuel burn.
That's kind of misleading as you wouldn't be able to generate the horse power at cruise that you potentially can at maximum rpm. It all depends on the maximum available HP at the cruise rpm.

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Old 03-16-2014, 10:25 AM   #32
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O C Diver,
That's true but it's close enough for what we're doing here I'd say.

Frequently information is useable and beneficial when you throw out the details that make most people say "what are you talking about?".
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Old 03-17-2014, 07:32 AM   #33
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The problem is the propeller that accepts 100% power at 100% rated RPM, looses its HP absorbing ability VERY rapidly .

Dropping down a few hundred RPM will lower the load a HUGE amount, which is why engine builders attempt to get you to prop for the pin, and then operate at lower RPM.

For engines that service lots of applications the builders RPM for generators for emergency or prime power production make the most sense to use.

Emergency power is short term, days or so, Prime is 24/7 forever.

Most engines come with 4 sets of power graphs , from 24/7 to sport fish , climbing up on the plane.

Each RPM will have a power rating .

The 24/7 rating for LRC makes the longest life setup.

But operating at a very small percentage of the 24/7 rating is not recommended at Cruise RPM.
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Old 03-17-2014, 09:11 AM   #34
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Additionally, the chart that TT provided us with is not a really good example because that engine produces about the same hp from 2100 on up. A more typical NA engine would not have the flat area at the upper end of the curve. If TT were to overprop to where his new red line is, and limit his RPM to that point (usually reseting the stop on the pump) he would, in his case be giving up very little HP because the curve is so flat at that point.
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Old 03-17-2014, 06:29 PM   #35
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Additionally, the chart that TT provided us with is not a really good example because that engine produces about the same hp from 2100 on up. A more typical NA engine would not have the flat area at the upper end of the curve. If TT were to overprop to where his new red line is, and limit his RPM to that point (usually reseting the stop on the pump) he would, in his case be giving up very little HP because the curve is so flat at that point.
I think that power curve is pretty typical. Attached is another one from a Deere 6090 rated for near continuous operation. The same engine rated for continuous duty has the same curve shape.

But your point is taken about the HP being nearly flat after the engine reaches peak torque. There is an argument that says you should prop to intersect the line at peak torque (and not go over). What I don't know is what happens to engine life expectancy when you run at the Crankshaft power curve rather than the Propeller power curve. I image it must go down or we would all be propping that way.
Attached Files
File Type: pdf Pages from 6090AFM75_B_M2_AP.pdf (396.8 KB, 29 views)
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Old 03-27-2014, 08:04 AM   #36
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>I agree. But why is that different from an M2 running 24x7 at 65% load factor? To get a 65% load factor on an M2, you need to drop the RPMs to 1850. Shouldn't it be 2100 just like M1?<

To change the LOAD the usual method is to select a load , gen head , water pump size or Propeller that fits the desired load at the desired RPM..

Its not just throttle position.

Thats why matching the engine loading , RPM , cruise speed and prop is more work than simply propping like a ski boat for full RPM at full throttle.

A 2100RPM engine would usually be run at 80% load at 90% of Rated Rpm.

The compromise of 1800 for cruise at 80% power (for 1800RPM) will usually result in very long engine life with high efficiency.

Low RPM operation is sometimes limited by the eng mfg , some fall off the chart at 1500 , so that would be the designed LR cruise, with the chart HP available at 1500 as the guide for loading.

Contemplating this concept shows how so many boats have far bigger engines than required , and mostly get by quite well as the HP rating is auto, tractor , or yard implement , flash peak BS,, not industrial.
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Old 03-27-2014, 10:21 AM   #37
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I've gone through two or three props to find my diesel's sweet spot--best thing I did was reduce my prop's pitch and bring everything within specs. WOT for my Volvo MD2030 is 3600 per Volvo specs (3200 - 3600). I cruise at 2900 RPM which is 80% WOT or 52.6% load according to Volvo's load/RPM graph. Volvo recommends 300-500 below WOT for cruise but this is simply too noisy and uncomfortable.
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Old 03-27-2014, 10:36 AM   #38
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Our CAT 3116 has a recreational "E" rating, max RPM 2800, cruise 2400. However the 2400 spec is way to high for how we use the boat. At 2400 she is plowing along at 10 knots trying to get up on plane, burning 9.7 GPH. We have found our sweet spot a 1600-1800, which gets us 7 or 8 knots burning a bit over 3gph. I think most of the turbo charged diesels are cruise rated for planing boats, not FD or SD trawlers. Contrary to popular legend, we have found no issues with running our CAT at the slower speeds. Almost 2k hours on the clock now with no problems.
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Old 03-27-2014, 11:27 AM   #39
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FF says;
"To change the LOAD the usual method is to select a load , gen head , water pump size or Propeller that fits the desired load at the desired RPM.."

Fred there's no such thing as "desired rpm". Unless you have a variable pitch prop the load is fixed. The rpm to load to is exact. The rpm where your engine develops it's maximum power. 3000rpm in my case and I need to prop to that engine speed as closely as possible. Preferably any variation should be in the underpropped direction as in 3050rpm being preferable to 2950rpm.

Your cruise prop notions are like trying to drive a diesel truck around in high gear. Not for normal people and normal boats.
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Old 03-27-2014, 12:52 PM   #40
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I turn my engine on....pull out of the marina and 5-12 hrs later having run at the same rpm and generally the same load all that time, then pull it to idle when I dock and shut it off.

Trucks are in high gear when rolling down the highway at cruise speed (50-80).....if they pulled away from the loading dock got pushed to speed by a helper and cruised flat lands for the whole trip with no stops and coasted into the next loading dock...I bet they would have one gear.

What's the diff?
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