Oil in lower unit

[amishboy]

Here's a thought. Instead of pumping oil into the fill hole on the bottom of the lower unit, which results in lost oil and a mess...

Why not fill through the top hole until oil flows out...run the unit to warm up the oil and break bubbles, then repeat?

Anyhow, wouldn't the space taken by an air bubble likely be smaller than the oil spilled while trying to get the cap screwed in?

What am I missing?

 

[QC]

Re: Oil in lower unit

What am I missing?

Getting the plug in fast enough appears to be the only thing you're missing . . .

Is this an I/O or OB? I should probably move this to the appropriate section (either).

 

[lcmains1]

Re: Oil in lower unit

Go ahead and try it your way and run it... let us know how it turns out.
I'll bet the new lower unit will be expensive

 

[dockwrecker]

Re: Oil in lower unit

Maybe your nickname should be "Slowhand"...

 

['78 Crusader]

Re: Oil in lower unit

Here's a thought. Instead of pumping oil into the fill hole on the bottom of the lower unit, which results in lost oil and a mess...

Why not fill through the top hole until oil flows out...run the unit to warm up the oil and break bubbles, then repeat?

Anyhow, wouldn't the space taken by an air bubble likely be smaller than the oil spilled while trying to get the cap screwed in?

What am I missing?

Go ahead a video tape this one....gotta see it.

In theory, ya that might work but as a practical application, you'll have more of a mess on your hands than anything. If you're not pumping the oil in too quickly, you should have a minimum amount of spillage if done properly.

 

[Utahboatnut]

Re: Oil in lower unit

If you are willing to take the risk on your lower/upper not having adequate lubrication you can do it that way. I prefer to use the mfg. reccomendation and fill from the bottom hole. Then top off what little you may lose from reinstalling the bottom plug. Get one of the pumps that attaches to the top of the lube bottle and screws into the lower hole fill till it weeps out of the upper vent hole(if applicable) and have cardboard and a rag under the lower for when you replace with the plug. Then top off and you are done.

 

[Fordiesel69]

Re: Oil in lower unit

Fluid needs to replace the air that is trapped in the lower unit. Where is the air going to escape? If you have all winter to add an ounce a day, by the end of the season it may be full.

One word, "DON'T"

or this will result:
http://rides.webshots.com/photo/2638711480044425697NvRPnv

 

[Home Cookin']

Re: Oil in lower unit

Here's the real reason: because we always done it this a way.

 

[amishboy]

Re: Oil in lower unit

Well Dockwrecker, as the Most Interesting Man in the World says, "there is nothing a man can do fast that a woman enjoys."

Although nobody said it directly I see what I was missing. The cavity will not fill because the air below the oil has nowhere to be pushed. What if the fill hole and vent were adjacent and the cavity design was such it pushed the air up thru the vent.

Design Engineers are so well educated but seem to be shy of common sense.

 

[Fed]

Re: Oil in lower unit

Fill it from the bottom with a screw in pump then put the top plug in then undo the pump and put your thumb over the hole until you're ready with the bottom plug in your other hand.

 

[Home Cookin']

Re: Oil in lower unit

then you'd be adding an extra hole, because you still need the drain, and the lower unit is not a place for a lot of holes. Any tiny vent tube inside the existing fill hole would clog with the oil.

I was filling mine recently and so frustrated at the mess I was making, and not having 5 hands, that I tried sneaking some oil in through the top. Doesn't work but for less than an ounce.

 

[paultjohnson]

Re: Oil in lower unit

Here's the real reason: because we always done it this a way.

R U a politician ?

Anyhow... Just try to picture all the air in the lower unit having to sloooooooowwwwwwwwwwwllllllllly bubble up thru the tiny orifice that allows gear oil to flow from the lower to the upper [or vice-versa] That little hole sealed by the quad ring. Whilst the top of that orifice is blocked by thick gear oil. I think FDDSL69 isnt far off on his time frame. Be sure to replace the top plug 1st and be quick, you shouldn't lose more then a half tablespoon doing it the proper way

 

[Art Bernard]

Re: Oil in lower unit

Fill from the bottom hole, any air is pushed out the top hole, also if you have rear trim/tilt move the engine back and forth a bit to work out as much air as you can. Reinstall top screw, quickly remove pump and reinstall bottom screw. Wipe up any spilage and your done. You can't go wrong doing it like that. If your worried about spilage out of the bottom hole, have you ever held soda in a straw by holding your finger over the top of the straw? Same principle, spilage will be minimal if you've put the top screw in correctly.

Art

 

[oldjeep]

Re: Oil in lower unit

If you are making a mess, then you are doing it wrong. There is not much spillage unless you are way overpumping when filling, forgetting to put the vent plug in before removing the pump from the drain/fill hole, or really slow putting in the drain/fill plug.

 

[ziggy]

Re: Oil in lower unit

amishboy still hasn't said what kinda drive he's working on. or maybe it's an outboard. we don't know..... kinda hard to say much when were left in the cold as to what to comment on...
for my i/o, it's filled from the bottom and i see no reason to reinvent the wheel. obviously in my case, for my i/o in my sig, there is a reason to fill from bottom up.

as for the op's drive.... maybe he's got a omc. who knows...

 

[Sixmark]

Re: Oil in lower unit

We do it this way because otherwise it would disrupt the natural ecosystem of the bacteria living in the lubricant....too much air would kill some of them and they would no longer eat the crud that develops on the gears, so in turn the gears would become rusty and then fail.


Don't try to reinvent the wheel, just do it the way it's supposed to be done.

 

[Stachi]

Re: Oil in lower unit

The OP asked a reasonable question , it's one that always puzzled me as well. We both learned the 'why' to do it. Thank You to those that explained why , and how to do it correctly. Your knowledge and patience are appreciated.

 

[NYBo]

Re: Oil in lower unit

Fill it from the bottom with a screw in pump then put the top plug in then undo the pump and put your thumb over the hole until you're ready with the bottom plug in your other hand.

Bingo! Spillage will be minimal using this method.

 

[444]

Re: Oil in lower unit

Bingo! Spillage will be minimal using this method.

Ya I do it that way too and I don't make any mess. Put the top plug in before you take the pump off the bottom. When the top plug is replaced, the vacuum will keep 99.9% of the oil in. Just block off the few drips with your thumb.

 

[Frank Acampora]

Re: Oil in lower unit

The engineers are way ahead of you. been there, done that, bought the tee shirt: On outboards, the larger ones of old Force, some OMC, and some Mercs have three plugs: A bottom drain, a top fill, and next to it a vent. You drain the oil by removing all three plugs. You replace the drain plug, and fill through the fill until oil comes out the vent. You wait about 1/2 hour for air bubbles to rise. You top off the oil and replace fill and vent plugs.