# Merc 25 sea pro - lower unit oil accumulation - Advice needed



## el9surf (Dec 23, 2008)

I have been noticing a slight oil residue accumulating out of the secondary water pickup under the cavitation plate, as well as on the bolt direcltly below the base of the prop. I'm still in the break in process and running double oil. 

I'm wondering if this is excess 2 stroke oil that hasn't burt, or if it is lower unit oil that is leaking.

Any tohatsu experts might be able to chime in since this is really a tohatsu with merc stickers.

Pic 1 
looking up under the cavitation plate. Notice the round secondary water pickup plate, it has the black ridges and single screw on the bottom of the cavitation plate. The residue is acccumulating here.

Also notice the bolt directly under the base of the prop. There is a tiny slit in the lower unit by design. Oil residue is slowly coming from this space and accumulating at the bottom side of the bolt.



















Any help would be appreciated. I'm thinking it is not anything to worry about but I would rather get a definite answer before I go run it again.


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## el9surf (Dec 23, 2008)

Just for reference there are no signs of visible damage to anything. I bumped a sandbar at idle the other day but it wasn't enough to take paint off the skeg.


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## el9surf (Dec 23, 2008)

nevermind 
I did a search on tohatsu 25 2 stroke break in and found the following.

Tohatsu 2-stroke outboards use TCW3 oil which is specially formulated for 2-stroke outboards. Do not use automotive motor oil or any other type of oil in your Tohatsu 2-stroke outboard. We do not recommend mixing different brands of oil (or even different kinds of oil of the same brand). The mixing of different brands of oil may cause gelling which may cause blockage of the filter screens. This could lead to serious engine damage due to the lack of lubrication.

As a result of running your outboard with a double-oil mixture, it is normal for your engine to emit more exhaust smoke than normal. You may also notice oil coming from the around the prop and/or from the exhaust relief port hole (located near the top of the lower unit) during this period. This is completely normal and you should see this excess oil eliminated once you finish your break-in period and resume the normal 50:1 oil/fuel mixture


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## Guest (Sep 8, 2012)

That's going to happen after then break-in period as well so don't freak out.


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## DuckNut (Apr 3, 2009)

And don't use automotive motor oil.


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## el9surf (Dec 23, 2008)

> And don't use automotive motor oil.


Yeah the fact that tohatsu had to specify this was somewhat entertaining. That just means someone has done it in the past and screwed up their engine.
I didn't remember my old merc 25 2 stroke doing this so I figured I would post it up.


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## rkmurphy (Nov 2, 2008)

> That's going to happen after then break-in period as well so don't freak out.


Yep had a late 90s Merc 25 2 stroke that did the same thing. Completely normal.


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## DuckNut (Apr 3, 2009)

These pictures are the poster child for 4 stroke. Stop the polution.


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## cutrunner (Jun 8, 2010)

It leaks oil on purpose.
Its to lube the outside of the lower unit so water doesnt stick to it, causing less friction :-X


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## el9surf (Dec 23, 2008)

The oil shown in the picture is the total accumulation from a week of sitting. Once I'm back to 50:1 I'm hoping this clears up significantly. I never noticed this on my old merc 25 2 stroke. I think it was a 2000, or 2001 model.


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## cutrunner (Jun 8, 2010)

I gotta put a tray under my lower unit on my 70hp johnson.
The first time i ran it and stuffed it back in the garage i saw a oul spot about 6inches in diameter on the ground


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