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Veem Interceptor Blade Strips

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

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  1. Maxwell

    Maxwell Senior Member

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    We replaced the Michigan 4 blade propellers on our 42 Open this week with Veem Interceptor 5 blades. There is noticeably less vibration when running and we picked up .8-1kt at cruise. However with 3/4 fuel, full water and the tender, the boat was making 2315 rpms at WOT when the engines are rated at 2350, so we're a little over propped. They're working on getting me the different Interceptor Strips which should fix the problem. On Veem's site, it says they can be changed in the water. Does anyone here have experience or suggestions with having a diver do it vs a short haul of the boat? My mechanic is willing to dive, however if its considerably easier to do on the hard then I'll go that route.

    Appreciate the suggestions..

    Lady Sam Veem.JPG
  2. Pascal

    Pascal Senior Member

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    Picked up 0.8 to 1 kt at cruise. How much where the wheels? :)
  3. Maxwell

    Maxwell Senior Member

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    Definitely not a cheap date... we had been chasing cavitation burn with the original props since I bought the boat (used) and finally decided to just get new ones to fix the problem. The prop shop wasn’t confident repairing the old ones would be trustworthy, but we’ll keep them as get home spares.
  4. Capt Ralph

    Capt Ralph Senior Member

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    They go out/in just like gaskets in a window frame. You will need some visibility. One of our divers has experience doing them but even then, prefers the boat in the slings for 30 minutes.
    In your future, ensure a Veem shop works on them to preserve the notch. In horror, I have witnessed other shops just grind the strips away and return a non-trim-able wheel.
  5. chesapeake46

    chesapeake46 Senior Member

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    Nice. Now I know how my wife feels when she sees some types of jewelry !
  6. DOCKMASTER

    DOCKMASTER Senior Member

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    Please post what you decide on change method and more importantly the results. I just put on Veems and whereas I currently don’t need to change pitch I’m very curious how well changing the strips really works in case I want to adjust pitch sometime. Thanks!
  7. DOCKMASTER

    DOCKMASTER Senior Member

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    Any update on how you changed the strips and what difference they made? Thanks!
  8. Maxwell

    Maxwell Senior Member

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    The boat is currently 5 hours from where I bought the props (and their diver). Having never actually changed one, I decided that diving it and changing myself is probably a bad idea. I’m having it short hauled a week from today to change them out in the slings.

    Will test and report back next week.

    Max
  9. rtrafford

    rtrafford Senior Member

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    My hunch is that the knot gained is seen in higher fuel consumption. Sounds to me like the boat being overpropped slightly has it working a bit harder at cruise as well. IF it's overpropped at WOT, it's overpropped at cruise. Not much of an issue if it's an easy cruise, but it doesn't take much loss of cup (or strips in this case) to find 50 RPM.
  10. rtrafford

    rtrafford Senior Member

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    Note that changing the pitch on these wheels can create a distortion in the groove shape, possibly bring issues in retaining the strips. I once changed pitch significantly in a set and simply welded the strips shut.
  11. Capt J

    Capt J Senior Member

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    On an electronic diesel where cruise is 80% load on the engine computers. I've seen over and over that being slightly overpropped slows down cruise speed (SOG), versus being slightly underpropped. Especially in MAN's and MTU's, that don't make the brute torque that CAT's tend to make. Even rated at 2300 rpms, the dealers like them to see 2350 rpms WOT with full fuel/water. The faster you spin the engines at 80% load the more boost and horsepower you make and spinning the props faster generally creating more lift, equating to a faster cruise speed. Obviously within reason, and you don't want a 2300 rpm motor hitting 2400 rpms WOT. I've found that at 80% load the engines burn what they burn, within a few gph.
  12. mapism

    mapism Senior Member

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    2000 Series MTUs are actually rated for 2450 rpm.
  13. Sea Gull

    Sea Gull Member

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    On new props it would be pretty easy to change them in the water. They slide out toward the root. The only complicating factor is that you have two strips on each blade, but I expect you’ll put all white ones back in, so reinstall is easy.

    After the props have been in service and you start to get some marine growth in the slots it becomes harder to slide the strips. It once took me an hour on a workbench to replace 10 strips.

    Another option is to shave down the orange strips with a razor knife.
  14. PacBlue

    PacBlue Senior Member

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    Overpropped on a marine engine rated at 2300 rpm results in a two way test average of 2299 rpm. 2315 rpm is not over-propped at all but right on the mark , the bandwidth is about 2300 - 2350. This helps absorb varying loads, heat and humidity as well as high sea temps.

    There is no such thing as over propped at cruise as long as you are within engine specifications, and the only way to check that is at WOT. You can cruise at 60/70/80/90% load, it’s your engine. The time at those loads is defined by the engine manufacturer.
  15. rtrafford

    rtrafford Senior Member

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    My basic principle of thought here is that if your prop is more efficient, or if it's simply pushing more water per rotation due to pitch or diameter or blade surface, that there is a direct relationship between that outcome and horsepower. If you're pushing more water at identical RPM, you're encountering more load, and therefore burning more fuel, even if slight.
  16. rtrafford

    rtrafford Senior Member

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    Sure there is. Engines are designed to follow a specific load curve based upon RPM/horsepower production. You can wreck an engine by overloading it at any RPM.
  17. PacBlue

    PacBlue Senior Member

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    Not if you are within the engine specifications that I just referenced, 2300+ rpm at WOT, two way average. So you won’t be wrecking your engine.

    That will also put you on an acceptable load curve for warranty, etc.

    There are current instances where experienced owners want to maximum high end cruise by running higher pitch, that is, not even achieving 2300 or 2450 rpm (depending on engine model) at WOT. They are propping to 2250 or 2400 rpm at the factory with the engine manufacturers approval. A light comes on if load goes over 100% to remind them to pull back the throttles.

    It’s all logged electronically so the manufacturer can tell if they are running at beyond 100% load and prevents them from “wrecking” their engine.
  18. Capt J

    Capt J Senior Member

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    THE OP IS NOT WITHIN ENGINE SPECIFICATIONS AND STATES THAT IN HIS INITIAL POST. He states that he is seeing 2315 rpms and his engines are 2350 rpm engines. So the OP is slightly overloaded by factory specs and rtrattford is correct in his thinking in this situation.
  19. PacBlue

    PacBlue Senior Member

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    So what engines do you think come in a 42 Tiara Open?

    And what engine do you even know of that are RATED 2350 rpm in that power size range? Go look it up if you don’t know.
  20. NYCAP123

    NYCAP123 Senior Member

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    C12 /2100rpm