Changing lower unit oil - New O-rings?

I plan to change the lower unit oil myself for the first time. Doesn't seem much to it and I read another post that says my '97 Merc Offshore 150 should hold about 22 oz of fluid. I originally bought a tube at Walmart but that isn't enough from what I read so plan to go to West Marine and buy a quart and a pump. From all the posts I read that is "the way" to do it.

Question is do I have to replace the o-rings when I do this? If so can I go to NAPA or Home Depot and just buy any o-ring that is the same size? I am going on vacation very soon and would hate to do this only to not be able to find replacement o-rings keeping me off the water.

Thanks guys!

Re: Changing lower unit oil - New O-rings?

Thoroughbred said:

I plan to change the lower unit oil myself for the first time. Doesn't seem much to it and I read another post that says my '97 Merc Offshore 150 should hold about 22 oz of fluid. I originally bought a tube at Walmart but that isn't enough from what I read so plan to go to West Marine and buy a quart and a pump. From all the posts I read that is "the way" to do it.

Question is do I have to replace the o-rings when I do this? If so can I go to NAPA or Home Depot and just buy any o-ring that is the same size? I am going on vacation very soon and would hate to do this only to not be able to find replacement o-rings keeping me off the water.

Thanks guys!

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The gaskets under the oil plugs sometimes split when re-used, or even overtightened. Some are pretty bad at that, some of them are tough and can be re-used successfully. Any marine mechanic will have them by the gross and be able to sell you a couple.

If the gear lube in it is green, it's probably mercury high-performance lube. Don't mix lubricants.

Another mistake often made is overfilling. Fill it from the bottom hole, then be a little slow disconnecting and putting in the screw. You want to lose about an ounce of lube. Without air space on top, it'll systematically blow seals and take on water.

hope it helps
John

Re: Changing lower unit oil - New O-rings?

j_martin said:

The gaskets under the oil plugs sometimes split when re-used, or even overtightened. Some are pretty bad at that, some of them are tough and can be re-used successfully. Any marine mechanic will have them by the gross and be able to sell you a couple.

If the gear lube in it is green, it's probably mercury high-performance lube. Don't mix lubricants.

Another mistake often made is overfilling. Fill it from the bottom hole, then be a little slow disconnecting and putting in the screw. You want to lose about an ounce of lube. Without air space on top, it'll systematically blow seals and take on water.

hope it helps
John

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It does help John, problem is I am no where near a marine mechanic so I have to do a lot myself which I don't mind but end up ordering parts. There is a West Marine near the office so I will try there and see if they have any.

If I were to check the fluid and it looked good should I just leave it? I have only put about 50 hours on the boat since buying it.

Thanks

Re: Changing lower unit oil - New O-rings?

Changing LU lube is considered an annual maintainance item, or more often with heavy use. When you drain the fluid you can easily detect moisture intrusion requiring seal maintainance. When you pull the lower plug, there is a magnet on it. If there is any more than a small amount of fine powdered iron on it, it would indicate abnormal wear, possibly a galled gear or bearing. That's the time for maintainance, not after you put the pinion out the side at sea. The only way to properly check the level is to fill it.

West has o-rings and gaskets in stock, but pricey.

You can order online from many places. Mercury parts here:

http://www.mercruiserparts.com/

hope it helps
John