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Dropped RPMS

Discussion in 'Post Yacht' started by bradlangdon, May 3, 2026 at 1:43 PM.

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  1. Capt Ralph

    Capt Ralph Senior Member

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    I fear it's another epidemic, contagious poor thoughts beyond factory specs to about every engine builder.
    It will never be found in any factory manual explaining a fine filter first.
    Even here in the swamps, at the stills, we understand course filters first.

    I did find that DDC secondary cartridge (filters that go into the metal housing) factory spec; 22 mic.
    The finest factory secondary (spin on) filter is around 10 mic.

    Old Detroits flow lots of fuel.
    Old Detroits can near burn anything other than water.
    High performance 6-71 would luv great fuel but what ever you are burning, it needs a lot of it flowing.

    But I have been drawn into a side topic and digressed.

    Please check the blower bypass hoses and install a pressure gauge on the last filter output rite before the engine.
  2. bradlangdon

    bradlangdon New Member

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    UPDATE! Went to boat last night and noted that there was quite a bit of black , slimy, algae looking sediment in the bowls on both Racors. The life span on these being changed is unsure so I am starting from scratch on that end. I am quite certain that this is bad enough to be the problem. I am sharing pictures as soon as I can upload them.
  3. YachtForums

    YachtForums Administrator

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    Brad, if you have trouble uploading the pics, send them to me and I'll add them to the thread.

    email addy removed
  4. bradlangdon

    bradlangdon New Member

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    Carl, just sent those pics to you so you can upload them. Thank you.
  5. YachtForums

    YachtForums Administrator

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    Here you go...

    Attached Files:

  6. Capt Ralph

    Capt Ralph Senior Member

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    That's not to bad but a great start.
    Send a pic of the media (filter).

    I use Paint to quickly downsize photos to less than 650 pix on my desktop.
  7. bradlangdon

    bradlangdon New Member

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    Capt Ralph, that was after whiping them out pretty good. the bottom of the bucket had alot in there. I am hoping that was it and I am sea trialing tonight.
  8. Greg Page

    Greg Page Senior Member

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    Have you been running bio-cide to keep fuel clean? Once it gets algee may need to have fuel and tanks cleaned?
    bradlangdon likes this.
  9. Capt Ralph

    Capt Ralph Senior Member

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    Why am I confused?

    By the way; 10 mic filters would be crushed in by now.
    d_meister likes this.
  10. Robertoman

    Robertoman Member

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    Capt Ralph, you are right about the 30 mic filters.
    I made a mistake when I typed about using the finer filters for primary filters.
    Happens every time I start drinking swampwater!
    You are not confused.
    Thank you for your knowledge
  11. Capt Ralph

    Capt Ralph Senior Member

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    I have the same problems with swampwater,
    rum,
    bourbon,
    vodka,
    diesel..

    If my Detroits can burn it, I can drink it.
  12. bradlangdon

    bradlangdon New Member

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    LOLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  13. bradlangdon

    bradlangdon New Member

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    I am now for sure, running biobor and Diesel Kleen .
  14. Capt J

    Capt J Senior Member

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    Skip the Biobor. You need water to grow algae, so first change your fuel fill o-rings to stop the water from getting in to begin with. Secondly buy "Clear diesel" from Power Service (they manufacture Diesel Kleen) but this works much better for your situation. Run 10 micron racors and be prepared to change them, this will get more of the Gloopy crap without having to change and prime secondaries (change secondaries every third racor change, every 2nd if running 30's). 30 Microns are outdated since we switched to the lower sulpher offroad diesel, it's too large of passages as the algae particles aren't as large as they used to be . CAT, MAN, VOLVO and other engine manufacturers now recommend and/or require (most require) 10 micron pre-filters. Call your local MAN,CAT, Volvo dealer and ask them if you don't believe it. After 2 tank fulls of Clear diesel, Then run a diesel biocide from Power Service (the company that makes Diesel Kleen) or continue clear diesel as it has a biocide in it.\

    Clear-Diesel Fuel & Tank Cleaner
    d_meister likes this.
  15. Capt Ralph

    Capt Ralph Senior Member

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    Modern, super high pressure, super fine injector tips, common rail pumps, super fast computer controlled injector valve require super finely clean fuel.
    Yes, Mfg's are requiring finer filtering solutions.
    None are recommending a change in filter schedules with finer first.
    AND, Detroit's do not require these supper fine and expensive filter plans.

    What I hope Skippy J is recommending with finer filter first is a temporary path until your ship's fuel and tanks are clean again.
    It might be convenient to just change the first filter knowing it will be trashed quickly.
  16. Capt Ralph

    Capt Ralph Senior Member

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    13 years ago I learned about snake oils. This is my aft fuel tank pick-up after my first use of these products.

    aft tank fuel pick-up 002a.jpg

    If you have a dirty tank, get it cleaned and fuel polished by a real shop.
  17. Capt Ralph

    Capt Ralph Senior Member

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    On my 12V71TIs, Detroit spec'd 30 mic and 16 mic. Always ran great.
    I added a middle filter that was between 17 & 20 mic with a water bowl also.
    Funny that that second water bowl was collecting water (Racor stopped using real fish oil).
    Still ran great.
    Then like a Stuff For Brains, I installed 4-5 mic (black filter) as a final secondary. Lost 300 RPM off the top.
    Going back to the factory 16 mic this weekend.
    20150525_184030 a.JPG 20250116_125629a.jpg 20250116_125709a.jpg

    Why I bring all this up? I think your secondary is rated around 20 mic.
    Your cannon bore injectors are going to starve during your cleaning process running 10 mic primary filters.