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Old 02-08-2013, 11:15 PM   #61
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Originally Posted by SeaHorse II View Post
I would have bet good money on that being the reason you want to go slower. Have you looked into getting a trolling valve? Have you tried lowering your idle to 650-700 rpm? That just might put you at 2.5 knots which is a speed I've caught a lot of salmon at.
No trolling valve available. I have a mechanical box. The hydraulic box only came with an 8 down angle on the output shaft.
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Old 02-08-2013, 11:20 PM   #62
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Getting back to the original post and comments by some that the govener controls engine speed , sorry but you are confusing a diesel engine to a gas craftsman lawnmower.the govener controls the amount of fuel injectected , the speed of the engine relative to the fuel injected is controled by the load, think of a pickup diesel engine as you go up the hill you still need to depress the accelerator pedal to overcome the additional load of the hill.hope that helps.
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Old 02-09-2013, 12:14 AM   #63
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I just kick it in & out of gear when in the marina. 850 does seem a tad high, though.
Yeah, in gear when making turns in the marina, and out of gear on the straight-of-ways when needed to reduce speed.

About 850 RPM is my JD's idle speed. At about 1000 it generates half its horsepower and pushes the Coot about half its 7+ knot maximum speed.
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Old 02-09-2013, 01:02 AM   #64
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Mark,
About 1000rpm at full throttle but you can't go 1000rpm at full throttle.
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Old 02-09-2013, 01:08 AM   #65
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Mark,
About 1000rpm at full throttle but you can't go 1000rpm at full throttle.
Huh??? At full throttle (2400 RPM), the Coot slightly exceeds hull-speed, about 7.4 knots. Here we're moving at 6.3 knots at 1800 RPM (68 out of a maximum 80 horsepower):

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Old 02-09-2013, 01:46 AM   #66
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Our FL120s idle at about 600 rpm. With our now-pitched-down props this gives us an idle speed of about 3.5 knots. This is slow enough that there is no need shift in and out of gear. We carry this speed right up to the turn into our slip.

We learned a long time ago that too litle speed is worse than too much speed. We retain good rudder authority all the way into the slip and this combined with the ability to vary the thrust between the props make for very precise boat control all the wy through the maneuver. Plus it makes it much harder for the wind or current to take control of the boat.
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Old 02-09-2013, 01:56 AM   #67
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I much prefer approaching my berth at about one knot or less. Don't want to go faster than I'd want to hit the dock. Since my minimum in-gear speed is also about 3.5 knots, I'm often in neutral approaching the dock.
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Old 02-09-2013, 02:06 AM   #68
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I think gear ratios and the motor they are attached to make a big difference in idle speed. My volvos top out at 3600 rpm and at idle of 600 i am turning my pops at 16% of their max rpm. The guy next door with the cummins that tops out at 2600 and idles at 600 is turning his props at 23% of full while crusing through the harbor. When i put my boat in gear at idle there is a gentle swirl of water out the back and it slowly get to just under 3 knt. The neighbor with the cummins put his boat in gear and there is a larg rush of water out the back off he goes, in and out of gear to keep it slowed down 16% Vs 23% is a sizable difference. It is the RPM range of the motor thar really makes the difference and also drives us to use different ratios.
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Old 02-09-2013, 06:21 AM   #69
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Getting back to the original post and comments by some that the govener controls engine speed , sorry but you are confusing a diesel engine to a gas craftsman lawnmower.
Sorry but your explanation is oversimplified, like the lawnmower. If we take that explanation to its end, your example engine is controlled by ankle rotation in response to inner ear and visual inputs.

There are as many control schemes as there are applications.

Limiting-speed governors control the idle and maximum speed settings
of the engine. The intermediate range is controlled by the position of
the throttle linkage.

Variable-speed governors that are designed to control the speed of
the engine of the throttle setting.

Constant-speed governors maintain the engine at a single speed
from no load to full load.

Load limiting, to limit the load applied to the engine at any given
speed to prevent overloading the engine at whatever speed it may be running.

Load-control, used for adjusting to the amount of load applied at the
engine to suit the speed it is set to run.

Pressure regulating, used on an engine driving a pump to maintain a constant inlet or outlet pressure on the pump.
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Old 02-09-2013, 10:41 AM   #70
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Originally Posted by RickB View Post
Sorry but your explanation is oversimplified, like the lawnmower. If we take that explanation to its end, your example engine is controlled by ankle rotation in response to inner ear and visual inputs.

There are as many control schemes as there are applications.

Limiting-speed governors control the idle and maximum speed settings
of the engine. The intermediate range is controlled by the position of
the throttle linkage.

Variable-speed governors that are designed to control the speed of
the engine of the throttle setting.

Constant-speed governors maintain the engine at a single speed
from no load to full load.

Load limiting, to limit the load applied to the engine at any given
speed to prevent overloading the engine at whatever speed it may be running.

Load-control, used for adjusting to the amount of load applied at the
engine to suit the speed it is set to run.

Pressure regulating, used on an engine driving a pump to maintain a constant inlet or outlet pressure on the pump.
Great summation Rick. For those who seek the cruising prop route, are there any governors that could be retrofitted (at great expense most likley) to existing engines?
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Old 02-09-2013, 11:50 AM   #71
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It is not a toy boat surveyor's job to approve or disapprove anything on your boat. He should keep his opinions to himself unless you ask, otherwise his role is to document condition so far as can be determined by visual examination. Period.

Unless the surveyor is representing a class society and is conducting a survey related to the vessel's classification or statutory status he has no mandate to bless or condemn anything.
Rick, on a related question, would adverse effects of over propping be evident in elevated EGT when running at lower cruising rpms? Put another way, is it possible to experience adverse effects w/o an increase in EGT? Delfin is slightly overpropped and runs at around 475 degrees at cruising rpm with the sensor downstream of the turbo in the dump tube (I think). Not sure it's relevant, but the max EGT is 875 degrees at 90% of rated rpm, which is all I can get with the current pitch.

Thanks...
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Old 02-09-2013, 12:14 PM   #72
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Third-Reef,
Good and very applicable point and over propping just narrows the range.
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Old 02-09-2013, 01:35 PM   #73
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Great summation Rick. For those who seek the cruising prop route, are there any governors that could be retrofitted (at great expense most likley) to existing engines?
Set screw on throttle linkage....
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Old 02-09-2013, 03:51 PM   #74
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Set screw on throttle linkage....
Thank you ps, now will the real Rick please stand up.
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Old 02-09-2013, 04:08 PM   #75
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I'm 700 rpm and 3.8 knots. I don't have a problem with the 3.8 as I just kick it in & out of gear when in the marina. 850 does seem a tad high, though.
what engine did you say you had?
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Old 02-09-2013, 06:49 PM   #76
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[QUOTE=markpierce;133318]
About 850 RPM is my JD's idle speed. QUOTE]

If i'm not mistaken the book idle speed for the JD 4045 is 650 RPM. 850 sounds high, for any diesel. The higher the idle speed the greater the chance for transmisson wear as you slip in and out of gear.
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Old 02-09-2013, 07:47 PM   #77
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[QUOTE=sunchaser;133470]
Quote:
Originally Posted by markpierce View Post
About 850 RPM is my JD's idle speed. QUOTE]

If i'm not mistaken the book idle speed for the JD 4045 is 650 RPM. 850 sounds high, for any diesel. The higher the idle speed the greater the chance for transmisson wear as you slip in and out of gear.
I just looked this engine up and this is what the jd manual says. But I think the 850 is in neutral with no load

IDLING ENGINE
Avoid unnecessary engine idling. Prolonged idling may
cause the engine coolant temperature to fall below its
normal range. This, in turn, causes crankcase oil dilution,
due to incomplete fuel combustion, and permits formation
of gummy deposits on valves, pistons, and piston rings.
It also promotes rapid accumulation of engine sludge
and unburned fuel in the exhaust system.
Slow idle speed for this engine is 800850 rpm at
factory. If engine must be left running more than 3 or 4
minutes, minimum engine speed should be 1200 rpm.
DO NOT allow engine to idle longer than 5 minutes.
NOTE: Generator set applications where the governor is
locked at a specified speed may not have a slow
idle function. These engines will idle at no load
governed speed (high idle).
S11
http://www.google.com/url?sa=t&rct=j...G_dEXlVbPaLzQQ

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Old 02-09-2013, 07:55 PM   #78
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Hmmmm...650...850...anyone oiut there that actually OWNs a JD care to share????
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Old 02-09-2013, 07:59 PM   #79
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[QUOTE=sunchaser;133470]
Quote:
Originally Posted by markpierce View Post
About 850 RPM is my JD's idle speed. QUOTE]

If i'm not mistaken the book idle speed for the JD 4045 is 650 RPM. 850 sounds high, for any diesel. The higher the idle speed the greater the chance for transmisson wear as you slip in and out of gear.
It's likely my memory is lacking. But the engine seems happier at 800 or so.
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Old 02-09-2013, 08:03 PM   #80
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Rick, on a related question, would adverse effects of over propping be evident in elevated EGT when running at lower cruising rpms? Put another way, is it possible to experience adverse effects w/o an increase in EGT?
The first indication of overload is increased EGT. So, if your temperatures are remaining well below the maximum allowed you should be OK.

What engine do you have? The reason I ask is I would check that the EGT limit is measured at the turbo outlet where it is relatively cool compared to the turbine inlet. The TIT is the highest you will measure, it reads higher than there than a pyrometer installed in the exhaust collector or manifold immediately after the exhaust valve.

If you have never done it before, make a note of the EGT in straight and level cruise with the wind and waves on the stern then, without changing throttle setting, turn around and put the nose into the weather and see what the temperature is through the maneuver and after steadying back on a reciprocal heading. If you are anywhere near to having load problems you should see a marked increase in EGT.

Watch the EGT while you make a few 360s, see how it changes in response to the increased load. That will tell you how much margin you have as well. I suspect that unless you are very much "overpropped" and/or have a dirty hull and prop, you won't seem much increase while maneuvering.
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