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Veem Interceptor Blade Strips

Discussion in 'Props, Shafts & Seals' started by Maxwell, Aug 8, 2020.

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  1. PacBlue

    PacBlue Senior Member

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  2. Maxwell

    Maxwell Senior Member

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    They are C12 715 hp per side.

    I’ve only run the boat a few hours with the new props and the burn rate seemed about the same as before, burning 24-25 gal/hr per side at cruise in relatively calm water... however the cat displays only use whole #’s, so if it varied either way by a fraction of a gallon, I wouldn’t know. I’m going to take on fuel this week and will run the boat before and after we change the strips then report back.

    max
  3. PacBlue

    PacBlue Senior Member

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    The interesting thing from a technical perspective is that the Veem Interceptor strips change the “effective” pitch. The baseline pitch is locked in by the metal geometry and the plastic inserts act like Interceptor trim tabs and change the water flow off the blade face giving a bigger “bite” without a lot of penalty. The efficiency gain in effective pitch should not be too bad for your fuel burn.

    And per the CAT C12 715 metric hp (705 brake hp in American terms) all you really have to be concerned with on an owned boat is to be on the other side of 2300 rpms, even if is just a few, as your boat should be all outfitted with your gear , equipment and fuel and water.

    Then you can use the CAT displays to find sweet spot on economy or maximize your cruise speed as you monitor load.
  4. mapism

    mapism Senior Member

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    Set them in liters, and you get a much higher accuracy.
  5. leeky

    leeky Senior Member

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    Here's a great (IMO) website for converting the liters back to gallons as well as lots of other conversions; YF member Marmot posted this many years ago: http://unitconversion.org/
  6. FlyingGolfer

    FlyingGolfer Member

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    Overpropped defined as taking too much bite of the water?
  7. Capt J

    Capt J Senior Member

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    More or less. Pitch is measured in inches in USA. In a perfect world with no propeller slip, a propeller with 32" of pitch would move the vessel forward 32" with each revolution. Too much pitch is similar in being over-geared or in a manual car, being in 1 gear higher than what you should be in.
  8. Maxwell

    Maxwell Senior Member

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    I took on fuel and ran the boat on Sunday. In less than 1' waves, we made 2315 rpm and 2297 in the other direction with 2 people on board, full fuel, full water and a 600lb dinghy on the lift. We decided to haul it today as Thursday when originally scheduled is supposed to blow 30 kts. The strips were easy to change out and we were only in the Travel Lift for roughly 25 mins. I'm sure there's a trick to it, but definitely think changing them in the water would be far more difficult as you really need to keep pressure on the strip while you slide it into the groove to make sure it is all the way seated as it enters the channel on the prop.

    We went and tested after with the same fuel load/crew and sea conditions as Sunday. This time we made 2325 and 2315 rpms respectively with no noticeable difference in fuel consumption or speed. The load on the motors at WOT was 96%. With the Cat C12's being rated at 2300 and the boat being at its heaviest, my mechanic is happy with the results and said to keep an eye on it in different sea states and as we burn off fuel etc. Does this sound like the correct approach?

    I appreciate everyone's feedback and will let you know how things go moving forward.

    Max
  9. Capt J

    Capt J Senior Member

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    Just out or curiosity, how are you air and fuel filters? Are they all clean? The rpm's make sense but the 96% load doesn't make sense......should be 99-1000% load I would think from experience.
  10. DOCKMASTER

    DOCKMASTER Senior Member

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    I'm confused. Your original post said you are rated at 2,350 rpm. Your latest post says 2,300. I'm assuming the 2300 is a typo if you are getting 96% 2325 and 2315?
    Based on 2,350 rated, can you adjust more by changing strips or are you at limit? Is your mechanic a CAT dealer? I wonder if CAT would so OK? Still seems like you are over propped to me. Maybe not an immediate pressing issue but something I would still look to correct if it were my boat.
  11. PacBlue

    PacBlue Senior Member

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    You look good to go, what was the Air and Sea Temp btw, typical August stuff?
  12. PacBlue

    PacBlue Senior Member

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    The CAT C12 is rated 715 mhp @2300 rpm.
  13. DOCKMASTER

    DOCKMASTER Senior Member

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    So if 2300 rpm rated you should be good. Really, you were pretty good before and really good now. My understanding from CAT when we just dialed in my new C-18's is the engine load % is an algorithm from calculated (not measured) fuel consumption so it's not always going to be exact.
  14. mapism

    mapism Senior Member

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    Correct, but beware: calculated doesn't mean inaccurate.
    I mean, if you compare the modern "calculated" way to show fuel burn with the old school flow sensors on feed and return lines (Floscan, Maretron or similar stuff), the main difference is that the latter also keeps into account (hence could be an early indicator) for instance a higher fuel burn due to worn out injector noozles.
    But other than that, the "calculated" logic is actually extremely accurate, because essentially it considers whatever the ECU decides to feed to the engines at any given second, based on the throttle position and several other parameters, and just translates the ECU instructions into GPH numbers.
    So, while it makes sense to call it calculated and not measured, actually there is no estimate involved, and malfunctioning aside, it's the real deal.
    Besides, also flow sensors do have tolerances, but that's another story of course.
  15. Maxwell

    Maxwell Senior Member

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    The air filters were cleaned maybe 20hrs ago and fuel have maybe 400 gals run through them as they were done last fall and we didn't splash the boat until just a month or so ago. I'm planning on changing them in the next couple of weeks and have some Dent vacuum gauges that we're going to install.
  16. Maxwell

    Maxwell Senior Member

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    Air temp was around 72 and sea temp 75ish.
  17. PacBlue

    PacBlue Senior Member

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    Running in Freshwater or Saltwater?
  18. Maxwell

    Maxwell Senior Member

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    Fresh... Ran 2 ways in the ship canal in Sturgeon Bay WI
  19. rtrafford

    rtrafford Senior Member

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    Less buoyancy without the salt, means less lift and more load...I think...
  20. rtrafford

    rtrafford Senior Member

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    Exactly. His initial post that prompted responses was that his engines are rated 2350, and he's turning 2297 to 2315. He agrees in that post that he's overpropped. I simply responded that if an engine is overpropped at WOT it's overpropped through its range. That isn't ideal.

    Now it turns out he has C12 Cats? That's 2300, not 2325 for the C15/3406E-800, not the 2350 mentioned as rating.

    So, if it's truly a C12, then the rating is 2300, and he isn't overpropped at all. Seems right on. Best case is she's just a hair loose at full load, and that seems to be what is being reported here.