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Old 13-08-2007, 01:10   #16
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This site may be useful. Click on wiring diagrams. Looks like a universal diagram for all their engines and the resolution is pretty crummy.

Universal M-12 Images and Specifications - Universal Diesel Engine Owners Manual - Marine Diesel Direct / Torresen Sailing Site
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Old 13-08-2007, 01:32   #17
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OK, you will firstly have to downgrade your estimated waterspeed. 6.6 kts is theoretical and will not be an actual. 5 kts would be more likely. This is because of several factors. Theoretical is based on wave length theory and does not contain other influences that come into the real world of a boat in water causing displacment and friction. The problem is that the wave length is changing the closer you reach the theoretical point of max. The Friction if the Hull in the water influences the shape of the wave. So the waterline is effectively shortening and a bow wave is developing that the bow is trying to rise up over. The result is the last 10% of speed costs 90% of the energy.
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Old 13-08-2007, 05:57   #18
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Couple more questions.

The wiring diagram,(Universal Diesel Engine Owners Manual - Wiring Diagram - Marine Diesel Direct / Torresen Sailing Site) shows the tach wired to an output from the alternator, the other wires on the tach are common to the other gauges. Does the tach convert an output from the alt to show rpm, or how does that work?

The whole theorectical hull speed thing is a bit confusing so I just accept it for what it is. However, the other day we had 7.4 (that was short lived but we maintained the high 6's for quite some time) on our fish finder with a paddle wheel sender. We were heeled over fairly good but not excessive so wll increases?


BTW this site has been really educational, thanks.
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Old 13-08-2007, 08:52   #19
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On diesel engines tachometer signal is generated by one of 3 things: 1) the alternator, 2) the magnetic sensor, which counts gear teeth, or 3) a Hall effect tachometer signal generator that is spun by the mechanical take-off.

An alternator Tachometer is energized by the pulse frequency generated by the alternator, which in turn is dependent on the alternator's rotor speed. These tachometers will have to be adjusted and calibrated to accommodate the alternator pulley ratio, and number of poles.

The diesel alternator tachometer (Dark Grey wire) is hooked up the AC (Stator) tap of the alternator. This connection can be marked as: W, AC, AUX, S, R, TACH, or nothing at all.

See also:

VDO Tachometer:
http://usa.siemensvdo.com/NR/rdonlyr...mmDiameter.pdf
And:
http://www.sso-usa.com/marine/Techni...Alternator.pdf

And:
Alternator Tachometer Signals - by Ample Power
Alternator Tachometer Signals
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Old 13-08-2007, 13:57   #20
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The only way to get a realy true speed reading is to use a GPS and run across an area that has no tide, across the tide, or in both directions and take the sum of the speed.

In regards to the tachometer, you need to ensure that it is calibrated. They have a means of settign them on the back and this needs to be done, or all readings are totaly erroneouse.
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Old 13-08-2007, 23:23   #21
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Quote:
Originally Posted by bmiller
However, the other day we had 7.4 (that was short lived but we maintained the high 6's for quite some time) on our fish finder with a paddle wheel sender. We were heeled over fairly good but not excessive so wll increases?
Wheels speaks the truth about hull drag and theoretical hull speed. Looking at my speed table it took 500 RPM to get the last .4 kts while motoring and I suspect 6 kts will about about all I'll get under motor.

However under sail we routinely see 6.5kts and the GPS has captured 7.8kts as our max speed.

Somethings going on! I suspect it is very complicated to explain and has something to do with increased water line and the wake shape when heeled over by 20+ degrees.
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Old 13-08-2007, 23:58   #22
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Quote:
Somethings going on! I suspect it is very complicated to explain and has something to do with increased water line and the wake shape when heeled over by 20+ degrees.
Yep that is exactly what is going on. The hull shape is such that when heeled over, the WLL is longer. Different designs will benifit from this affect in with varying results. But the curve of the hull sides gives the affect of a longer length. Plus the power is applied to the hull at a different point, and helps "lift" the hull from the water along with the Rudder which applies a lot of lift (can be as much as 10%) and some keel designs can apply lift as well.
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Old 15-08-2007, 17:59   #23
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Follow up. The engine will reach rated max in nuetral. Breather is clean. GPS speed matches speed on fishfinder. Guess I'll just be happy with 5knots at 2200rpm. We must have a pretty aggressive prop.
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Old 16-08-2007, 03:54   #24
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When in gear, you should be able to briefly pull 3200RPM if your prop is correctly pitched. At 2200, you are way over pitched. This does several things which are all hard on the poor engine. Having the correct pitch will also change several things, notibly, give you more "zing" in her step around tight manouvering area's, better acceleration and most likely, improve economy. But most importantly, it will most likely increase your boat speed. Why? well you are not achieving your engines rated Hp at 2200. In fact, you may be a good 50% down on Hp.
I suggest next time you haul out, you get the prop repitched. It is a reasonably easy and painless job and well worth the effort.
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Old 16-08-2007, 04:44   #25
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For every 1 inch of pitch change, expect a change of approximately 200 RPM.
(Less Pitch = More RPM, & vice versa).

After the break-in period (approx 25 hours at 75% cruise speed), an average cruising speed for a sail boat installation is about 80% of the maximum engine speed obtainable, to achieve hull speed .
(ie: Max. 3600 x 0.8 = 2880 Cruise RPM)

Universal M12 Specifications:
Maximum: 3600 RPM
Cruising Range (Approx.): 2600 - 3300 RPM.
Goto:
Universal 200157 Owner's Manual - Marine Diesel Engines Marine Diesel Engines and Engine Parts from Torresen Marine's Marine Diesel Direct - Yanmar - Westerbeke - Universal - MASE
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Old 16-08-2007, 06:51   #26
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Great info, thanks. Where can I get a prop re-pitched? Is a new prop about the same price? I live in Colorado and marine service centers are hard to come by.
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Old 16-08-2007, 13:35   #27
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Can't help you with where, but repitching is not greatly expensive. Waaaay cheaper than a new one.
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Old 06-08-2012, 16:43   #28
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Re: M12 black smoke under load

Did you ever figure out the cause. I have the same problem. Thanks for any info you can give me
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