1968 Mercruiser 120 oil leak @ upper shift shaft

[Fisch]

I recently did a water pump repair on my Mercruiser 120 (pre-Alpha, MC-1) and had it out Tuesday ... everything is/was seemingly wonderful ... that is, until I noticed a small circle of oil in the driveway.

Further detective work revealed that this oil is coming from the upper portion of the shift shaft in the bell housing (I believe) ... and it very small ... a very minimal drip.

Fearing that some sort of seal had been compromised, I drained the oil today to look for signs of water and ... NONE.

Question being, is this a big deal? Sometimes normal on an old unit? Should oil even be in this part of the drive? If not, possible places it could be coming from? How labor intensive is a repair, if that's necessary?

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

Well ... upon further review, I presume that the exhaust bellow is bad, after running her on muffs this afternoon and seeing a slow water drip near the front most part of the bellow (near the transom).

I also saw a slow water drip from the same spot that the above mentioned gear lube came from. Now, while it would seem logical to see water there if the exhaust were traveling through this area, oil would not. Is it likely a seal is blown if oil is somehow in here? What seal is most likely?

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

 

[jerryjerry05]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

That spot is a non oil area.It is just a connection point.If it's dripping anything it's probably unburned gas and carbon.The second is probably a bad hose clamp.Nothing to worry about on either one.
Just keep an eye on your gear lube.LOTS OF $$$$$Put in a resivoir bottle.Cheap security.J

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

Not familiar with the reservoir bottle ... interesting, I'll look into that.

As for the oil ... it's definately gear lube (which is brand new after the water pump work) ... caramel brown, thick and oily. No two ways about it. This is where I'm most baffled, although I am admittedly a novice despite owning this thing for about 8 years.

 

[jerryjerry05]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

You need to get it pressure tested.To find the leak.Sometimes the front seal will leak into the top bellows.Get that checked.J

 

[Eric 3.7LX Alpha 1]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

Here is a photo of the other side of that shift shaft which you see water and lube leaking from out of the bellhousing,

{courtesy of Fishermark} .

As you can see that shaft runs thru the exhaust passage in the bellhousing. The lower brass bushing doesn't seal anything.

The upper brass bushing is also a seal to keep water from inside the exhaust from getting inside the shift cable area.

There should not be any lube in that exhaust passage but water passing thru would be normal.

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

OK ... so I'm deducing that the front seal is potentially shot? Don't know what a seal job runs, but from what I've read it seems that this is something typically left to the pros, no?

Is the seal in question the one pictured in the picture above? If so, would this being bad normally allow oil into the exhaust and water passage? Is the bushing Eric mentions exposed to oil, and if the bushing were bad would this potentially lead to oil getting down the shift shaft?

 

[dubs283]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

potentially a leaking u-joint bellows

water in the bellows could find its way down through the seal for the shift shaft in the bell hsg

possible yoke seal leaking into the u-joint bellws as well (hence the oil water mix)

is the oil leaking drive lube??

did you pressure test the drive after you serviced the h2o pump??

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

No means of pressure testing, so no.

Last night after running it a bit on muffs, water showed up. Oil did not show back up until today, and only a couple of drops. Whatever it is, it's very slow ... and yes ... 100% without a doubt, gear lube. Smell and the whole nine yards.

 

[Don S]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

Remove the outdrive, youw ill see where it came from.

 

[Fisch]

Re: 1968 Mercruiser 120 oil leak @ upper shift shaft

Remove the outdrive, youw ill see where it came from.

Yeah ... which is where I feel I'm ultimately headed ... was just hoping that someone may have crossed this road before, and I could determine if I was capable or if it's a more shop-worthy endeavor.