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Oil sending unit

Discussion in 'Carver Yacht' started by 1000 islands, May 5, 2015.

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  1. 1000 islands, May 5, 2015
    #1
    1000 islands

    1000 islands Member

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    I just changed the oil on my Mercruiser 7.4 and there is no oil pressure showing on the gauge.

    Where is the sending unit located ?

    I have changed them on various motors in older cars...1950's - 1980's

    I'm sure they must be similar.

    Thanks
  2. 1000 islands, May 6, 2015
    #2
    1000 islands

    1000 islands Member

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    74 views and nobody has an answer.....

    Come on guys
  3. AMG, May 6, 2015
    #3
    AMG

    AMG YF Moderator

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    I don´t have your engine, but I have Google and found out it is on the back of the block, usually with a light blue wire connected. Here or at the gauge it can be corrosion so this is what you can check first...
  4. Capt Ralph, May 6, 2015
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    left side of the engine (looking from the flywheel end), above where the oil filter or oil filter adaptor is.

    No oil pressure and it worked before? Did you change the filter?
  5. YachtForums, May 6, 2015
    #5
    YachtForums

    YachtForums Administrator

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    Maybe because YF's technical section is for larger motor yachts. Not the best place for Mercruisers. This thread has been moved to the Carver forum.
  6. 1000 islands, May 6, 2015
    #6
    1000 islands

    1000 islands Member

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    Yes I did change the filter and still no pressure on the gauge.

    I'll go look for the gauge tomorrow and see if there's a signal.
  7. NYCAP123, May 6, 2015
    #7
    NYCAP123

    NYCAP123 Senior Member

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    Sounds weird that it worked before and not after. Sorry for the dumb question here, but you did put in enough oil in and started the motor before looking at the gauge? My next guess would be that you accidentally knocked a wire leading from the sender lose.
  8. K1W1, May 7, 2015
    #8
    K1W1

    K1W1 Senior Member

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    Take the sender out, with the ignition disabled wind it over on the starter and see if any oil comes out. If it does you have oil pressure, if it doesn't you don't.
  9. ksbguy, May 7, 2015
    #9
    ksbguy

    ksbguy Member

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    Did you use synthetic oil for the first time? Synthetic oil has more detergents in it and it can dislodge build up in the block and clog senders. Pull the sender out, it's most likely clogged up internally.

    If motor stays running you most likely have oil pressure. There's an oil pressure switch that will kill ignition power on loss of oil pressure.