Lower Unit Gear Lube Question

[gitnby]

Changed out the oil on the lower units this weekend.

No problems on the pontoon outboard. Got in the kayak and did it while it was on the lift. Easy deal. Put a trash bag around the lower unit and drained it, replaced oil unitl oil flowed from upper hole. Put in top plug, and just a trickle came out of the lower hole as I removed the tube and replaced the lower plug.

On the bass boat, I decided to back it onto the lift, and change oil from the front of the slip.

Everything was good until I put top plug back in, and found that I couldn't get a good angle to remove fill tube and replace lower plug.

So, I trimmed motor up with fill tube still attached and as I pulled tube to replace lower plug, the oil came gushing out?

So, I assume the angle had something to do with that, as I have always done it with motor trimmed perfectly vertical, and it never did more than a little trickle.

Maybe lost 2 oz?

Should I pull bottom plug and pump more oil in, or not worry about it?

[GNSfishing]

I would add lube to be sure the proper amount was in the lower unit. The lower unit repair is not cheap and what ever extra lube you have to purchase will be a lot less in cost versus what a destroyed lower unit would cost to repair......

[fishinwrench]

Just remove the top plug with the motor level and stick a bread tie or end of a zip strip in there to see where the level is. If it is within 1/2" of the plug hole you're fine.

If you ever need to add just a little you can tilt the motor up and turn it so the top plug is facing up. Dribble in until full then lower motor and allow the excess to run out before replacing the plug.

You don't want to overfill a Merc/Mariner/Force lower unit because expansion pressure can pop out the cheesy little shift shaft seal.

[gitnby]

Thanks, fishin wrench! Great idea!

The motor is a 200 HP Johnson, so I guess I won't worry about overfill.

Plus, I really didn't want to stick a bread tie in my Johnson!

[Craig]

When I took my nerver in for lower unit oil the tech raised my motor all the way to keep the oil from coming out after I saw that now its SOP

[gitnby]

I assume he raised it AFTER he filled it, and the fill tube was still inserted? Otherwise, it's impossible to completely fill the cavity before it runs out the top hole.

That's exactly what I did, but for some reason, that oil just shot out of the lower hole like I've never seen?

[merc1997 Bo]

lower your trailer tongue to get more ground clearance on the lower unit. always fill until oil comes out top hole. insert top plug, have bottom plug ready to insert as you take oil tube out of bottom hole. loss will be minimal unless you drop the plug . in that case, cover hole with finger while you retrieve plug.

bo

[gitnby]

After thinking about all of this, I am wondering if maybe my top plug isn't seated properly or the gasket is cracked?

I've changed the oil on these things dozens of times and never had it gush out like that, which makes me thinks there is air getting in there causing it to flow out so quickly?

I went and bought a new plug and will top it off per fishinwrench's suggestion, and then put in new plug.

Thanks for all the suggestions, guys!

Never have had to replace a LU, and really don't want to find out how much fun it can be!

[GNSfishing]

That's a smart move, yes you must of had an air leak at the top plug. Those gaskets get old and can crack and not only let the lube out but also will allow water in. Vacuum is what keeps the lube from running out after you remove the feed tube. Don't tilt the motor up leave it vertical to add lube till it comes out the top plug hole. You need the air space to prevent blowing your seals from expansion. Air will compress, liquid will not. I would purchase several gaskets and store them in a dark place to prevent exposure to UV and you will be prepared for the next time. UV it very hard on any type of plastic and will deteriorate it over time.