Drain Plug Lower Unit O-Ring & Gasket Confusion

[dunz]

After changing the lower unit oil I have heard it is recommend to change the oil plug gasket and O-ring. Does this apply to new engines as well? The motor in question is a 2001 Mercury 90ELPTO. I don't remember seeing an O-ring when changing the lower oil, and if the gasket sits against the screw where does the O-ring go? Does this apply to the two vent screws as well? At $2.99 a gasket that can get expensive for all three screws. Also, someone mentioned the OMC plastic washers seal better than the Mercury fiber ones. Anyone know where I can order some from? Only ones I can find are OMC O-rings.<br /><br />Thanks for the help,

 

[bryanredfish]

Re: Drain Plug Lower Unit O-Ring & Gasket Confusion

The items you are referring to are one in the same. There is simply a small gasket that should be replaced. If you didn't see one when you took out the screw, then it's still stuck on the screw itself or the LU. The ones for my 2003 90 ELPTO are flattish and are red. I always use the Quicksilver gaskets, though you can get replacement versions at West Marine. By the way, whoever packaged these things are real marketing jerks. They only come in packets of 5, so you need to buy a 2nd package for the 2nd change.<br /><br />By the way, replace the gaskets (all of them) every time you change the LU oil. Also, I'd suggest that you purchase a shop manual for your o/b.

 

[andrewkafp]

Re: Drain Plug Lower Unit O-Ring & Gasket Confusion

Small price to pay to keep water out of your L/U.<br />Buy bright blue or red ones as they are easy to see when stuck in the recess. One of my Blue ones came out with the screw and rolled away Spotted it missing straight away.. Couldn't see any blue in the recess.. .

 

[dunz]

Re: Drain Plug Lower Unit O-Ring & Gasket Confusion

Originally posted by bryanredfish:<br /> The items you are referring to are one in the same. ... I always use the Quicksilver gaskets, though you can get replacement versions at West Marine.

The West Marine catalog is where the confusion comes from, it has both O-rings & gaskets. See West Marine Catalog Pg. 324 Which part do you think is correct?

 

[bryanredfish]

Re: Drain Plug Lower Unit O-Ring & Gasket Confusion

It's the blue one in the upper right hand corner. The o-ring is an after-market Tempo product. Stick with OEM equipment, or as close as possible.

 

[Hooty]

Re: Drain Plug Lower Unit O-Ring & Gasket Confusion

Some plugs use gaskets, some require an o-ring. If the threads go all the way to the bottom of the head, it uses a gasket. If there's a small gap between the threads and the bottom of the head, it taked an o-ring.<br /><br />c/6<br />Hooty