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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. bradlangdon, May 3, 2026 at 1:43 PM
    #1
    bradlangdon

    bradlangdon New Member

    Joined:
    Jul 12, 2025
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    Location:
    510 SW South Carolina Drive, Stuart
    1989 43 with 671 TIB's, I have seen it turn both 2400-2450. Bottom was inspected and cleaned and props look good. I have dropped down to 2100 on both engines at WOT, speed is way off of course as well, very little black smoke even when I get on the throttles heavy. One puff of smoke and it goes away at one second and then only hits 2100 on both. I just changed the primaries and secondaries, also removed air filters and cleaned them. In neutral , I am seeing 2575-2600 dead racking in neutral. Can anyone provide me with any potential issues that I have not thought of yet? Your help as always is very much appreciated.
  2. Greg Page, May 3, 2026 at 4:36 PM
    #2
    Greg Page

    Greg Page Senior Member

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    Mar 4, 2017
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    Location:
    Annapolis MD
    When one of the 6-71 TIB powered boats we looked at had low RPM the mechanic came and re-set/timed the injection racks.
  3. Capt Ralph, May 3, 2026 at 4:45 PM
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    Satsuma, FL
    Fuel filters..
    I have chased this problem before.
    Had it myself when I put in to fine of mid and secondary filters.
    No black smoke when the engines don't get fuel.
    Vacume and pressure gauges really help here.
  4. Capt Ralph, May 3, 2026 at 6:23 PM
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    When was the last time it made RPM loaded?
    What has been done since?
    Was the boat out of the water when inspected and cleaned then?
    What has been loaded into the boat since the last time it made RPM?
  5. boatpoor, May 3, 2026 at 8:24 PM
    #5
    boatpoor

    boatpoor Senior Member

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    You say the props look good but what do they feel like? If the feel like 40 grit sandpaper or worse, that will rob a lo of RPMs.