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detroit 671 ti low oil pressure

Discussion in 'Ocean Yacht' started by canepole, Aug 5, 2016.

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  1. canepole, Aug 5, 2016
    #1
    canepole

    canepole New Member

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    Can someone shed sum light on 671s having low oil pressure at idle about 5500. It seems to only have 4 or 5 pounds of pressure engines have only 350 hrs. rebuilt by J&T.Otherwise, run great. From some other post it seems to me a lot of people have had the same problem.
  2. RT46, Aug 5, 2016
    #2
    RT46

    RT46 Senior Member

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    do you mean 550 rpm?

    thats pretty low for idle.

    does the oil pressure increase with engine speed?

    Is the alarm going off?

    can you check oil pressure with a mechanical gauge?

    can you check tacs?

    at idle and warmed up the 671 does not make a lot of oil pressure.
  3. Capt Ralph, Aug 5, 2016
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    71s need about 5 psi warm. Please ensure your using CF-2 / 40w oil.
    When your making horsepower, you should see 30+(40?) psi on oil pressure.
  4. RT46, Aug 5, 2016
    #4
    RT46

    RT46 Senior Member

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    agree
  5. Capt J, Aug 6, 2016
    #5
    Capt J

    Capt J Senior Member

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    550 rpms is a bit low. I'm not super familiar with 671's as it's been years since I've run a set. With 12v71's which I've run lots of, it's very common for them to have 2-8 psi of oil pressure at dead idle in gear, after running at cruise. This is measured by the gauge on the dash which isn't nearly as precise as a mechanical gauge within feet of the engine room. One yacht with a lot of hours we had to change the alarm senders from 5 psi to 2 psi. But had one with a fresh rebuild from the dealer with all D.D. parts that would sound the alarm for a few seconds when shifting in and out of gear after the oil was hot with a 5 psi alarm sender. I've noticed the Shell 40w seems to lose more oil pressure (after 50 hours on the oil) than other brands. I prefer the Mobil Delvac 40W in D.D. 2 strokes.
  6. canepole, Aug 6, 2016
    #6
    canepole

    canepole New Member

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    yes 550 rpm at hot idle. oil pressure does increase with engine speed. alarm only on starboard but both are right at 5 psi. what is a correct idle rpm for that engine ? next step will be to put a gauge on engine. I am looking at buying this boat and everything else checks out ok, however I am not anywhere close about a ten hr. drive away. That's why I am trying to get all the info I can before making another trip. And a real thanks to everyone that has replied this is a real help to me.
  7. Capt Ralph, Aug 6, 2016
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    I remember 550 was the warm idle for 71s. Hard to keep sometimes when engaging the clutch.
    On those older DDs that have a time with the clutch & governor, I bump the idle up a bit to 550/600 rpm in gear. Sometimes 1/4 turn on the buffer screw is enough (be careful here).
    Usually resulting in a neutral idle around 600 to 650.
    Twin Disk clutches should not be engaged over 750 rpm.
  8. K1W1, Aug 7, 2016
    #8
    K1W1

    K1W1 Senior Member

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    In my youth I fitted a few 2 psi switches to 8V 71's to over come the problem when the vehicles were hot and they came to a halt, some needed it and others didn't.