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06-21-2016, 08:50 PM
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#1
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Guru
City: Punta Gorda, fl
Vessel Name: Escapade
Vessel Model: Nordic Tug 37 2002
Join Date: Jan 2015
Posts: 1,231
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Fuel Filter Reduce WOT?
Would a plugged secondary fuel filter make you lose 300 rpm from normal WOT?
I changed the Racor 75900 primary with no rpm change.
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06-21-2016, 09:11 PM
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#2
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Guru
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,835
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My limited experience with plugged filters is that the performance continues to degrade quickly. IOW, it gets worse, the lower rpm level doesn't remain constant. Certainly hurts nothing to change it and cost is pretty minimal.
When was the last time you cleaned or inspected the hull and running gear?
Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
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06-21-2016, 09:11 PM
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#3
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Guru
City: Here
Join Date: Sep 2012
Posts: 2,940
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it could.
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06-21-2016, 09:23 PM
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#4
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Guru
City: Gig Harbor
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 9,046
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Quote:
Originally Posted by Pgitug
Would a plugged secondary fuel filter make you lose 300 rpm from normal WOT?
I changed the Racor 75900 primary with no rpm change.
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Also you can kick up some debri in the process of changing the primary that the secondary could have picked up.
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06-21-2016, 09:47 PM
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#5
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 3,023
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I have seen several instances where reduced fuel flow reduced top rpm (in other people's engines).
I have vacuum gauges after my Racors and pressure gauge after the lift pumps. It makes it easy to tell when filters are getting dirty. Always with enough advance warning to plan the filter changes.
If you have dual primary filters that can be switched running, put a 2 micron in one and a 30 in the other. Run on the 2 until it starts to plug, switch to the 30. Do this a couple times and you'll have super clean fuel and tanks. I buy clean fuel and I run on 2 micron primaries all the time. Use biocides and conditioners.
I carry 2000 gallons and it only took one 2 micron change.
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06-21-2016, 09:50 PM
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#6
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Guru
City: Stuart FL
Vessel Name: Lucky Lucky
Vessel Model: Pacific Mariner 65
Join Date: Aug 2013
Posts: 2,760
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With Racor pressure gauges, what RPM should the engine be running when you check the gauge?
__________________
Howard
Lucky Lucky
Stuart, FL
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06-21-2016, 10:22 PM
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#7
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Guru
City: Gig Harbor
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 9,046
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Quote:
Originally Posted by hmason
With Racor pressure gauges, what RPM should the engine be running when you check the gauge?
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I like the gauges that have have drag indicators. They will show the highest vacuum that you have achieved. That way you can check the gauge with the engine off before or after to have run the engine.
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06-22-2016, 05:37 AM
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#8
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Guru
Join Date: Oct 2007
Posts: 22,553
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"and you'll have super clean fuel and tanks"
Clean fuel will not strip decades of grunge from inside a fuel tank , unless the boat spends much of its time in quite rough conditions .
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06-22-2016, 08:14 AM
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#9
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Guru
City: Punta Gorda, fl
Vessel Name: Escapade
Vessel Model: Nordic Tug 37 2002
Join Date: Jan 2015
Posts: 1,231
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Quote:
Originally Posted by hmason
With Racor pressure gauges, what RPM should the engine be running when you check the gauge?
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WOT should be 2800 but all I get is 2450.
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06-22-2016, 08:54 AM
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#10
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Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,188
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Quote:
Originally Posted by Pgitug
WOT should be 2800 but all I get is 2450.
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In addition to above suggestions, a few more preliminary things to consider: - Is this a new happening?
- If 1 is yes, what did you do "last" in the way of maintenance or just messing around?
- When was last full RPM under load achieved?
- If 1 and 2 are yes, retrace steps in 2.
- Have you verified RPM with a photo tach?
- Yes, buy a Racor vacuum gauge and install it.
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06-22-2016, 09:17 AM
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#11
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Guru
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
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You could also have a fouled/damaged propellor, or the wrong pitch propellor if it has been this way since you owned the boat.
__________________
George
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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06-22-2016, 09:39 AM
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#12
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Guru
City: Gig Harbor
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 9,046
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Sunchaser asks all the right questions. If this is a new phenomenon then look to something like a fuel filter. If you are just noticing now, then it could be a bunch of things including being overpropped by a bit. FWIW, I don't hit max rpm either, I am shy by about 200rpm. This was done at the sea trial. Not sure why, I could be over propped slightly.
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06-22-2016, 01:49 PM
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#13
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Guru
City: Punta Gorda, fl
Vessel Name: Escapade
Vessel Model: Nordic Tug 37 2002
Join Date: Jan 2015
Posts: 1,231
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Quote:
Originally Posted by dhays
Sunchaser asks all the right questions. If this is a new phenomenon then look to something like a fuel filter. If you are just noticing now, then it could be a bunch of things including being overpropped by a bit. FWIW, I don't hit max rpm either, I am shy by about 200rpm. This was done at the sea trial. Not sure why, I could be over propped slightly.
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At the sea trial we hit 2725. So I know that a proper pitched prop would read 2850. But now I am at 2400. A few weeks ago I was 2450. So I am guessing it's the secondary fuel filter since I changed the primary Racors.
Today I did change the secondary and flushed a few larger dirt particles out of the old filter. So next time out I will see if we have gained some ground.
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06-22-2016, 02:33 PM
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#14
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Guru
Join Date: Jun 2008
Posts: 5,040
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Well I can tell you that when I had my ex boat with the new Cummins 6BTA, I once had a reduced rpm situation due to some filter clogging.
It was a very subtle rpm reduction, but non the less due to a filter that needed changing. (which I did later that day after we anchored up for the night).
So that certainly CAN be a cause.
I did not have a vacuum gage on that system so can't help you out with a number.
__________________
Jay Leonard
Ex boats: 1983 40 Albin trunk cabin, 1978 Mainship 34 Model 1
New Port Richey, Fl
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06-22-2016, 02:35 PM
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#15
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Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,188
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Photo tach readings would be useful?
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06-22-2016, 02:39 PM
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#16
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Guru
City: Gig Harbor
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 9,046
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Quote:
Originally Posted by Pgitug
At the sea trial we hit 2725. So I know that a proper pitched prop would read 2850. But now I am at 2400. A few weeks ago I was 2450. So I am guessing it's the secondary fuel filter since I changed the primary Racors.
Today I did change the secondary and flushed a few larger dirt particles out of the old filter. So next time out I will see if we have gained some ground.
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Let us know what you find out. Also, if you don't already get a vacuum gauge on your Racors.
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06-28-2016, 11:30 AM
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#17
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Guru
City: Punta Gorda, fl
Vessel Name: Escapade
Vessel Model: Nordic Tug 37 2002
Join Date: Jan 2015
Posts: 1,231
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I have a gauge between my Racor 75900 pair. It has a drag needle that has never gotten to the red.
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06-28-2016, 11:53 AM
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#18
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Guru
City: Gig Harbor
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 9,046
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Quote:
Originally Posted by Pgitug
I have a gauge between my Racor 75900 pair. It has a drag needle that has never gotten to the red.
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Great. I would look at replacing the filters though if the gauge ever gets to about 7mmHg.
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06-28-2016, 12:10 PM
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#19
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Guru
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,835
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Quote:
Originally Posted by Pgitug
I have a gauge between my Racor 75900 pair. It has a drag needle that has never gotten to the red.
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You may want to talk to a Cummins dealer regarding the safe limit as the gauge warning has no relationship to the vacuum pump limits. For my "C" series Cummins my dealer said the Cummins lift pump had a significantly lower vacuum tolerance before the pump would fail. Don't remember the number, but once I see the needle move on a full tank of fuel, it's time to change the cartridge. It's changed annually regardless. Compared to fuel, the cartridge costs nothing (<$10). The "B" series is more vacuum tolerant, but it would be wise to know Cummin's limit.
Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
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06-28-2016, 12:17 PM
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#20
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Master and Commander
City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,559
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The one time I couldn't reach WOT, the first thing I checked was the Racor. Switching to the second Racor resulted in immediate solution.
__________________
Kar-KEEN-ez Koot
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