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Oil pressure sensor

Discussion in 'Engines' started by anchorsaway, Aug 1, 2024.

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  1. anchorsaway, Aug 1, 2024
    #1
    anchorsaway

    anchorsaway New Member

    Joined:
    Mar 22, 2021
    Messages:
    6
    Location:
    michigan
    my oil pressure alarm went off the other day on my 871 Detroit so I replaced the pressure sending unit now at idle the gauge reads 100 psi at cruise speed it goes to the normal 55 pounds I wonder if I got a bad sending unit ! any thoughts?
  2. Capt Ralph, Aug 2, 2024
    #2
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    13,389
    Location:
    Satsuma, FL
    Standard American senders and gauges (SW) work one way.
    European senders and gauges (VDO) works bass ackwards.
    Some European senders and gauges (VDO) works like the American senders and gauges (SW).
    All of these are installed on our boats, in the states.
    You purchased the wrong sender.

    Usually, with serial number, a real Detroit shop can sell you the correct part first try.
    A part number off of the original part may have helped.
  3. ranger58sb, Aug 2, 2024
    #3
    ranger58sb

    ranger58sb Senior member

    Joined:
    Aug 20, 2013
    Messages:
    895
    Location:
    Chesapeake Bay, USA
    Sending unit and gauges rely on matched resistance curves,
    10-180 Ohms and 233-40 Ohms being common examples. Note those example values are backwards from each other, much like the results you're seeing.

    Might be you need "the other" sender to mate with what your gauge should display.

    -Chris
  4. Thisisit, Aug 10, 2024
    #4
    Thisisit

    Thisisit Member

    Joined:
    Aug 20, 2004
    Messages:
    169
    Location:
    Midland, Ontario, Canada
    Just going to add my ingredients to this sender soup.
    I replaced all the gauges this spring with KUS instruments. Of note, there are two anomalies:

    1. Oil pressure gauges read backwards. This is due to incompatability with what are most likely OEM VDO senders. No big deal, I will simply order two compatable senders. I think Wema/KUS would be the way to go, ensuring the resistance readings are opposite to what I have currently?

    2. Temp gauges are reading about 20°F cooler when compared to the masters on the engines and to what the engines usually produce at 80% throttle. Would a compatable temp sender correct this? If so, does anyone have KUS gauges that can suggest a brand of temp sender?

    One other question... do master gauges in the engine room count as a second helm station, and if so, does that affect the choice of senders, as mentioned in other threads?