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Rebuild my 1981 - 46 Post Detroit 6-71 TI's

Discussion in 'Post Yacht' started by P46-Curaçao, Feb 17, 2016.

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  1. P46-Curaçao, Feb 21, 2016
    #21
    P46-Curaçao

    P46-Curaçao Senior Member

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    Curaçao (CW), Hollywood (FL) and Amsterdam (NL)
    Could you explain the difference in performance?
    (Double check tomorrow, I'm quoting from the survey...)
  2. Capt J, Feb 25, 2016
    #22
    Capt J

    Capt J Senior Member

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    He might have a different geat ratio than you as well though.
  3. P46-Curaçao, Feb 25, 2016
    #23
    P46-Curaçao

    P46-Curaçao Senior Member

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    I have the same ratio!
  4. RT46, Feb 26, 2016
    #24
    RT46

    RT46 Senior Member

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    good point on the gears.

    Mine are 1.5:1
  5. P46-Curaçao, Feb 26, 2016
    #25
    P46-Curaçao

    P46-Curaçao Senior Member

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    Mine are 1.5:1 too!
  6. Henry King, Jun 9, 2026
    #26
    Henry King

    Henry King New Member

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    It's been awhile since I wrote anything. I owned a 43 post, I already forgot what year but think it's 1987. I have twin 671 with turbo. Motor fires right up no smoke only if I push it hard I will get black smoke. My question to the forum is rebuilding it, because I don't think the motor will fit through the door! I was once told they would cut the back half, for me sounds like way more work. Since it still runs great, would the top half be a good idea or just try to rebuild it sitting in there. They didn't make it easy to move around in there, plus I'm a little over weight
  7. Capt Ralph, Jun 9, 2026
    #27
    Capt Ralph

    Capt Ralph Senior Member

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    White or grey smoke is un-burned fuel. From low compression by worn piston rings or leaking exhaust valves. This smoke will burn your eyes if you get your face close to it.
    This will be your indicator of requiring a rebuild.

    Black smoke is to much fuel per air (fuel rich).
    Not necessary meaning a rebuild but attention is required.
    So, Clogged air filters,
    Restricted air coolers (6-71TI & TIBs),
    Blowers not dis-engaging (TIBs),
    Low turbo boost,
    Exhaust restrictions,
    Over fueling injectors (blown tips),
    To much prop pitch per weight of the boat...
    Anybody mess with your throttle delays or modulators since it last ran clean?
    What service has been preformed since it last ran clean?
    Mother-in-law move lots of stuff on board?

    One or both engines puking black smoke?
    Does the black smoke ever clear up after 10 - 15 minutes on the pins?
    What HP tune (280 to 450+ HP)?
    What RPM are you turning @ WOT?
    Is the bottom really clean?

    There is no way we can help with out the whole picture unless you just want to know how to;;;; If the block is good, in-frame rebuild.
    A stripped down short block will fit thru your aft door on a long boom.

    Lets open a new thread if we need to continue these chats.

    Oh, Almost forgot;
    Post kids are cool,
    71s rule..☺☺
    Last edited: Jun 9, 2026
  8. Greg Page, Jun 9, 2026
    #28
    Greg Page

    Greg Page Senior Member

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    Can't say for sure on '46 but the PO who re-engined our '43 took the 6-71's out and put the new CAT C7.1's in through the doorway. Only removed the door from the track. Don't know if partially dis-assembled DD's coming out, but did say nothing was removed from the CAT's going in.
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