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Post 46 performance?

Discussion in 'Post Yacht' started by Eroc, May 4, 2014.

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  1. Eroc, May 4, 2014
    #1
    Eroc

    Eroc Member

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    Hi Post owners. I've decided to start looking for a boat, we are considering a 46 because of the two head layout which I'm sure is handy with kids and family on board not to mention A Post is undeniably on of the best looking sportfish made. I have had my eye on an 85 46' with 450hp 6-71's that have had recent rebuilds, the listing claims 22knt cruise. Is this accurate? Also was there a change in the galley layout in 85, were there any other significant changes in that era? Thanks
  2. RT46, May 4, 2014
    #2
    RT46

    RT46 Senior Member

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    Eroc,

    22kt cruise sound a bit high to me, but it really depends on what rpms is considered cruise speed.
    Some of the 46 Posts on this site cruse pretty close to that speed.

    I have a 46 with TIBs that weighs 48k pounds in the slings.

    The fastest I remember my boat going was 27 kts WOT in perfect conditions with the wind and tide behind me. The boat was also slightly overpropped at the time.

    I like to run the boat at 1950 to 2100 rpms depending on sea condition. My boat seems to run 17 to 20 kts at that speed depending on sea condition and load.

    I guess with a clean bottom and light load my boat would run 22kts at around 2250-2300 rpms but I don't run the engines that high except for short bursts to check wot under load.

    The two S/R and two head layout is awesome for family and guests.

    My 46 has the galley up.

    Overall I am very happy with the 46 Post and I would highly recommend the boat.

    The boat is very easy to work on and is very comfortable for its size.

    good luck
    RT 46
  3. Eroc, May 5, 2014
    #3
    Eroc

    Eroc Member

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    I figured that 22knts was high, your numbers are what I had in mind.
    The layout is well thought out, it seems that Post used the interior space better then other builders. Thanks for the response, everyone on here is great and I've learned alot from reading past threads
  4. AllanS, May 5, 2014
    #4
    AllanS

    AllanS New Member

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    Post 46 Performance

    My advice would be to look for a Post 46 II model that has the 6V92s. I think the 71s are great engines but operate at the top end of their performance limits in a this 24 ton boat if you want 22+ knots...even in this pretty flat bottom boat.

    I have a 1989 46' with the 92s. I love the fact that it jumps out of the water at 1600RPM. I usually cruise it at 1850-1900 (19-20Kt). The engines are loafing at this speed and they sound happy, never stressed. They still operate at 180 degrees so no problem with carbon buildup in the engines or on the transom. If I need the power to outrun a storm, I can do it. You just can't do that with the 71s, you need most of what they have to maintain a decent cruise.

    Fuel consumption...yeah, I'll burn a bit more but I like having the headroom even if I don't use it often.
  5. RT46, May 6, 2014
    #5
    RT46

    RT46 Senior Member

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    I agree, there is no question that the boat with 692s is faster

    There are some advantages to the 671TIBs, maintenance is less and easier on a straight 6 over the V6, fuel burn, turbo set up, dry vs wet liners, rebuild cost is less....
  6. Capt J, May 6, 2014
    #6
    Capt J

    Capt J Senior Member

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    I agree and it's been a while, but isn't WOT on 671 TIB's 2800rpms and cruise should be 2250rpm's? If I remember correctly and a slower cruise at 2200rpm's is fine with them all day long.....even 2250rpm's if they're propped right.
  7. Eroc, May 6, 2014
    #7
    Eroc

    Eroc Member

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    Although the increased speed from 6-92's would be nice I'm a big fan of 6-71's, as for cruising and max rpm I have no clue but would like to know, any input is appreciated. 18-20 knts is fine for me, if I'm looking to go faster a 50 would be my choice but out of my budget right now.
  8. AllanS, May 6, 2014
    #8
    AllanS

    AllanS New Member

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    Post 46 Performance

    I didn't target the 6V92s for speed. Like I said, I cruise at 18-20 knots, that is plenty fast for me. I just like the fact that if I need power, I have it. Fastest I've taken the boat is 26kts. I rarely go over 20.

    More than speed, I like babying these old engines. Cruising at 75% of rated capacity means that I am not overtaxing them. 1800RPM also is the sweet spot in the fuel curve.
  9. rgsuspsa, May 8, 2014
    #9
    rgsuspsa

    rgsuspsa Member

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    Rated RPM (Maximum Power RPM) for a 6-71TIB is 2,500. For best longevity of the engines prop the boat such that engines achieve nominally 2,600 RPM with clean bottom and running gear. When the boat is run with a less than clean bottom and props it should still be capable of reaching 2,500 RPM,
    which will avoid overloading the engines when cruising at 2,200 RPM or less.
    If the engines cannot make at least 2,500 RPM, they are overloaded and
    appropriate action should be taken to permit the 2,600 RPM capability to be restored, such as cleaning hull, props, running gear, etc.