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Old 06-28-2016, 12:41 PM   #21
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Originally Posted by Pgitug View Post
Would a plugged secondary fuel filter make you lose 300 rpm from normal WOT?
I changed the Racor 75900 primary with no rpm change.
It most certainly could.
Remove the secondary and cut it open, or just bang it on a paper towel upside down to see what kind of crud is in it.
If it is dirty, you need to improve your primary filtration. The secondary is a "last chance" filter that ideally will never see any high degree of contamination.
Seaboard Marine's website has articles you need to read, also some very good information on boatdiesel.com.
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Old 08-15-2016, 03:37 PM   #22
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I replaced my Racor primary fuel filters and still was 300 rpm from WOT. I then changed out my on engine secondary fuel filter and got back the 300 rpm I had lost. 👍😋
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Old 08-18-2016, 01:40 AM   #23
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Originally Posted by Pgitug View Post
I replaced my Racor primary fuel filters and still was 300 rpm from WOT. I then changed out my on engine secondary fuel filter and got back the 300 rpm I had lost. 👍😋
Pgitug,
You missed my point in previous message.
If there is significant debris in the secondary filter, your primary filtration is not up to the task.
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Old 08-18-2016, 10:12 AM   #24
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Originally Posted by kapnd View Post
Pgitug,

You missed my point in previous message.

If there is significant debris in the secondary filter, your primary filtration is not up to the task.

Not necessarily. I don't recall if Pgitug mentioned it, but how many times were the primary filters changed without the secondary being changed? We know from his earlier post that it was at least once. It is very possible to pass debri to the secondary in the process of changing the primaries. If this is done several times, it could add up to something significant. Plus, the specs for his engines if I recall, call for 10micron primary and 2 micron secondary. Again, I could be wrong on that. This would mean that even if the primaries are doing their job very well, that eventually the secondary could start to get plugged.

It sounds to me that the secondary was simply not changed often enough, but then I tend to change filters "too often".
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Old 08-18-2016, 10:12 AM   #25
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it could.
Of course it could. Any restriction in the fuel supply could reduce WOT RPM. Of course other things can reduce it as well but replacing the filter is cheap and easy and is probably in the engine's maintenance schedule anyway.
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Old 08-18-2016, 12:36 PM   #26
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Originally Posted by O C Diver View Post
...

When was the last time you cleaned or inspected the hull and running gear?

Ted
Can't see how a fouled hull can affect engine speed. Boat speed yes, but not engine RPM.
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Old 08-18-2016, 04:31 PM   #27
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Fuel Filter Reduce WOT?

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Originally Posted by markpierce View Post
Can't see how a fouled hull can affect engine speed. Boat speed yes, but not engine RPM.

A dirty hull is harder to push through the water, obviously. That in turn can create an overpropped condition, whereby the drag is just too great for the motor/prop combo, and RPM's can drop.... Don't ask me how I know... Ha.
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Old 08-18-2016, 05:23 PM   #28
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A dirty hull is harder to push through the water, obviously. That in turn can create an overpropped condition, whereby the drag is just too great for the motor/prop combo, and RPM's can drop.... Don't ask me how I know... Ha.
This is true and the warning is in my boat's owner's manual.
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Old 08-18-2016, 09:34 PM   #29
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My diesel engine doesn't slow when there is an increased load such as headwinds and waves. The engine controls operate a governor, and the governor controls fuel flow while maintaining a constant RPM while boat speed may vary. Gasoline engines don't act like this.
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Old 08-24-2016, 01:55 PM   #30
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My diesel engine doesn't slow when there is an increased load such as headwinds and waves. The engine controls operate a governor, and the governor controls fuel flow while maintaining a constant RPM while boat speed may vary. Gasoline engines don't act like this.
But it will slow when your engine can no longer make additional torque at a given rpm. That's what happens when dirty running gear prevents an engine from reaching rated rpms- at that rpm, the total load on the engine from drag (air and water) cannot be overcome by thrust from the propeller.
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