How Much Lower Unit Oil?

[This_lil_fishy]

1986 Mercury 50, 30 Cyl, 2 Stroke


I am planning on replacing the lower unit oil after changing out the impeller, and was curious, how much oil do I need? My local dealer sells it in one litre bottles only, and I don't want to buy too much. The dealer isn't very helpful, as they would prefer I pay them to do the work....go figure...


Ian

 

[Yepblaze]

Re: How Much Lower Unit Oil?

A quart is usually enough. It is pumped in from the bottom and is full when it runs out the vent.

You can buy a little hand pump or just use the pointed end of the oil container's cap to inject the oil. But if you decide to just squeeze the bottle method grab a second quart because you can only squeeze 2/3 of a quart till it won't squeeze anymore and some fancy hand work is needed to continued till full.

 

[This_lil_fishy]

Re: How Much Lower Unit Oil?

Thanks for the info, I was just going to purchase the pump, $11 worth of headache savings in my book. Scary, a full quart? When I drained it, I would say there was half that in there...maybe less. Guess I found my funny rattle noise at full throttle..or when slowing. Thankfully everything seems tight still..no grinding or slipping...yet! When I pulled the drain plug I noticed it had a coating of very very fine (powder like) filings...not a lot but enough...but if I hadn't of checked looks like I wouldn't have finished the fishing season.

How much play is normal in the prop shaft? (When you turn it left to right in gear). Maybe I should drop the lower unit and check.

Ian

 

[Yepblaze]

Re: How Much Lower Unit Oil?

It probably only holds a pint, but I buy it by the quart, and like to have extra on-hand for next year.

I usually pick up a couple. It's pricey for the good stuff at the Merc dealer, but that's what I use.

The plug may be magnetized and a bit of fine metals is usually ok.

Prop shaft can have play. If it aint leaking, and otherwise works ok, leave it alone

 

[This_lil_fishy]

Re: How Much Lower Unit Oil?

8.5 Fluid Ounces was in there, measured it. Put a bit more then that back in before it came out the vent. Thanks for the help, actually having extra is great, I forgot to take the old gasket off the drain hole, gonna have to drain a fair bit out by the time I get it off now...the vent tube gasket was real hard to get out. The old fluid was dark grey, almost black...probably never changed....go figure...


Ian

 

[shanew]

Re: How Much Lower Unit Oil?

If my memory serves me, that gear case holds 13oz. When you go to change those gaskets, if you have the top vent plug (or plugs) back in, the vacuum should hold most of the oil in the gear case. Whenever I change gear case oil, I always remove the prop and thrust washer, look for fishing line in the prop shaft seal, grease the prop shaft splines, and re-torque the prop. If you live in a cold climate always do this maintenance at the end of the boating season prior to the first freeze. If you have a bad seal and the gear case is full of water and it freezes, you get the picture. Good luck.

 

[mthieme]

Re: How Much Lower Unit Oil?

Also available is a hose with fittings on either end. One fitting screws into the LU. The other screws over the tubes. It also has a clamp on the hose.

iBoats has something similar with a pump in the middle.