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1990 Post 46 II RPM/Speed curves

Discussion in 'Post Yacht' started by Hoddinott, Sep 3, 2016.

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  1. Hoddinott

    Hoddinott New Member

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    Sep 3, 2016
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    Mystic, CT
    Hello, I bought a 1990 Post 46 II (PMC46218C090) last year and have been going through the boat refurbishing her systems, there's been a lot of band-aiding, but it's been keeping life interesting.

    She is powered with Detroit Diesel 6V92 TA's (6VF174092 & 6VF172826). I've been running some speed/RPM checks and she seems really slow to me. I'm running with full fuel and water tanks. She has 4-bladed (26"x24") props and makes 18kts at 1800 RPM and 23kts at about 2350 RPM. That seems slow to me.

    Can anyone with a similar engine/prop configuration tell me what your cruising and top speeds are?
  2. chesapeake46

    chesapeake46 Senior Member

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    Sorry, I only have '71's but congratulations on the boat. Good luck with it.
  3. Davidoc

    Davidoc Senior Member

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    Winter:Delray Beach, Fl Summer: Bahamas
    I have the same set up. JT's 550hp aftercooled.
    1850 = 19-20 knts depending on sea. At 2350 she did do 27 knts but not recently. Now she's loaded a little heavier with stuff and is in need of water and air systems cleaning. I am in the process of doing all that as we speak. I am running three blade props and can check the pitch and diameter tomorrow if you like. My gear has to be clean, clean to get that speed and rpm. It will take me a couple more weeks to get her outside for a run.
    I would not overlook the effectiveness of the coolant and the quality of the air going into the blower from the turbo. I am changing out the Walker Airsep filters and housings. I sent the turbo's out for rebuild, doing the blower and cleaning the after cooler. I sent out the heat exchangers and boost coolers to be cleaned. My symptoms were engines running a little too warm and not pulling my higher rpms. Did you have the engines surveyed? If so how did they do? Good luck.
  4. deanpe

    deanpe New Member

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    Hollywood, MD

    Where do you send heat exchangers to get cleaned? I have J&T 6-71TI's and need to get them cleaned.

    Thanks,
    patrick
  5. Davidoc

    Davidoc Senior Member

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    Broward Radiator. Ft. Lauderdale
  6. RT46

    RT46 Senior Member

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    Agree to all above.
    I have 71s but the same applies.
    the boat has to have a clean bottom, clean fuel, clean air, clean intercoolers, and clean exchangers to achieve maximum performance
  7. deanpe

    deanpe New Member

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    thanks!
  8. 2lrep

    2lrep New Member

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    hello and congrats! I've got a 95 with 550 6-92's as well, I'm not too sure of my props, the port motor has about 75 hours on it with a newly rebuilt turbo, the starboard has 900. Running last weekend with 1/2 tank full in the stern (500 gal.) and nothing on my forward tank and at 1850 I'm running 20-21 kts. 1950 around 23 and 2350 I'm at 29-30 knots without the enclosure up.
  9. Capt J

    Capt J Senior Member

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    I'm not a Post 46 expert. But how clean is your running gear? A little bit of scaling and such will really slow you down. Also how many layers of bottom paint do you have? If it's a 1/4" thick, stripping it, barrier coating it, and fresh paint will usually net you 2-3 knots if you've got a bunch of layers of bottom paint.
  10. Davidoc

    Davidoc Senior Member

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    Good advice from Capt J. I'd be pretty happy with those numbers for now.