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Oil Press Sending Unit

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OP gauge acting weird, so I bought a new sending unit. The parts guy at the dealer sold me a one-wire model for my 340 Monsoon 2005.

Now I look at my engine and see the sending unit above the oil filter has 3 wires, not one. Also, there is a threaded hole above the sending unit that is empty, no plug or anything. On the wire harness nearby is a blue wire with female post-type connecter that is hanging free, not connected to anything.

This all looks suspicious, like a switch should be screwed into the empty hole and the blue wire connected to it. Also, I'm assuming I should have received a 3-wire sending unit at the dealer since the existing part has 3 wires (?).

Please help if you're familiar with this stuff! Thanks

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Which oil sending unit are you changing, there are 3? A picture would be great for people to help you.

The blue wire hanging free is normal, I'm pretty sure.


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Did take pics, but can't figure out how to attach....dang computers.

There are 3 wires coonected to the one sending unit that is located just above the oil filter. I assumed only one sending unit - are you saying there are 3? If so, where are others located, and which one feeds the OP gauge?

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sounds like your low oil pressure switch is missing, and that may be the blue wire that is hanging.

to post the pictures, put them on some file sharing site like photobucket, copy the "img link" to the file, then paste it into your TMC message (the img tags will automatically be added to the link).

so it looks like this (this is a picture of the oil pressure switch - part number S645006):


Edited by jgouveia3
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Well the mysterious hole leave alone. Unless there is oil pouring out of that hole, it isn't going to measure oil pressure anyway.

In previous model year boats (I can't recall ever having to do an oil pressure switch on an 05+ boat) there were two switches at that location, both single wire. I think your best best is to pull the switch out and compare with what you have, and bring that back to the parts guy.

I'll make sure to take a look at my 05 this weekend and report back.

Also, loose the FRAM oil filters they are junk. Use a NAPA, ACDelco, or Mercury instead.


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