Leak

I'm new to the site. What a great resource.
I know its my first post but I need a question answered about a '96 15hp merc that I've had since new. I noticed a small puddle of oil under it the other day and never noticed one there before. Upon inspection I noticed the oil was coming out of a small hole in the lower unit but I can't tell if its threaded (see picture). My manual shows it as a hole and doesn't say what its for. With all that said what is it and is this normal? If not any ideas on a fix?
Thanks!



Different angle

Looks like that hole is about the same level as the top gear case oil plug/screw. I would guess it's some kind of drain hole for any residual water in the lower unit near the pump intake.

Just a drain hole for any water that gets traped in the lower unit.That is a merc feature.

Thanks guys!

scoobeb said:

Just a drain hole for any water that gets traped in the lower unit.That is a merc feature.

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scoobeb, I'm trying to think this through. How does it (drain hole) allow water out and not in? I guess I should ask it differently. To check the seals on a lower unit they put pressure on them, pumping a given amount of pressure and watching a gauge to see if it will hold this pressure for a given time. If this overflow allows water out without any pressure in the unit, how does it operate that the water would just come out but during a pressure check it wouldn't leak. And why is oil coming out now? Hope this all made some sense. Just curious? Thanks!

To be 100%honest i can't answer that question but i do know mercs of that same era have that hole as i had a 2001 15hp 2stroke merc and water always leaked out of it.Plus under the cavitaion plate on the sides of the lower unit there is 2 small drain holes also that water goes in and drains out.If it makes you feel better take it to a dealer as a good dealer won't charge to look at that.Call a dealer as they may no more.You can also just for good info not to knock anyones knowledge here but there is a few smart fellows at iboats that may be able to anwer your question.

I'm surprised no one else has chimed in on this as i would think some one would know a for sure anwer.I would try to im pappy he is a smart fellow on stuff like this.He has been around outboards for a long time it seems.I will try to do some research for you today to see if i can find some kind of anwer for you.

Also you see the bolt to the right of the hole that is in sight,there is a drain hole on both sides of the lower unit that is not visible in the pic because you would need to put the lower unit up and take a pic to see the 2small holes.

The hole is to drain cavities in the lower unit that is out side the gear case where the gear lube is.

crazymanme2 said:

The hole is to drain cavities in the lower unit that is out side the gear case where the gear lube is.

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Just asking again.....if these cavities are not within the the gear case area what is in them to drain out or how does liquids (water or grease) get there to drain out?

Another thought:
It seems hard for me to figure out why some company would design an engine with a hole allowing grease to drain out. When this product (outboard engine) is used like it's designed, is operating underwater, thus that same orifice that is supposed to drain grease, allows a very harmful substance (water) to the engine's drive train which is a sealed system? Again I'm just thinking out loud and not a mechanic........I'll admit sometimes I shouldn't think so loud!!! :wink:

I would assume that any oil coming out of a water drain hole is not a good sign.

My old two stroke would drain oil out of the prop, but I'm sure it was from the exhaust. That same motor had a lot of smoke coming out of the drive shaft area where it coupled to the lower unit and the inside of the cowling was always greasy and I assume some of it made it down into the lower unit but never saw it coming out of the drain holes.

Simple solution:call merc or call a good dealer in your area who knows about mercs if you are worried.I have done that a ton of times and merc has told me some good info.I don't think it's anything to worry about.But it's always better to be safe then sorry.I know it's some type of drain hole.