Mercury 115 (1985 tower of power) Oil leak around prop

[gewf631]

After searching the archives, and looking through my service manual, it appears that I may have some leaky prop shaft seals, but I wanted to query the collective knowledge of the iBoats forum before I start digging into anything. Motor is a 1985, 115HP, 6-cyl (model # 1115625)

After sitting over the winter in the garage, I noticed a small amount of dried oil under the skeg (patch was maybe 4 inches in diameter). Didn't think much of this, so went through all my usual season-start maintenance checks, and put the motor on the muffs. After letting it run for 15 minutes or so, I buttoned everything back-up, and garaged the boat. Pulled it out 2 days later, and had a similar size puddle of gear oil, so I pulled the prop and saw a small amount oil collected in the lower unit housing.

Replaced the water pump impeller a couple seasons ago (only get maybe 5 hours on the water a year), so it's probably due.

My search of the archives found a couple references to prop shaft seals, and looking at the Brunswick website, and the exploded view of this area, it appears the parts in question might be #'s 66 and 67 in the attached (Merc #'s 76868 for inner, and 70081 for outer). The 2 would only run about $20, but I don't want to start down an unnecessary path, or worse, one that I can't complete.- I read mentions about the difficulty in removing the gear carrier.

The archives mention pressure testing, so I suppose I can take the gear housing to a local dealer for this service (or is it easy to do myself?). Or, with the gear carrier in hand, is this an inexpensive fix for the shop?

Thanks in advance
Ed

 

[Mi duckdown]

Are you sure that it is not un burnt fuel/oil? was there water in the lower end?

 

[calvinator]

x2 on it being un burnt fuel/oil. Exhaust exits through the lower housing.

Take the prop off. Clean the prop shaft well and then put a towel under the prop shaft/seals. See if any oil leaks out.

 

[gewf631]

Thanks for the suggestions

Burnt fuel was my first thought as well, but the puddle definitely was gear oil. I cracked the screws but didn't see any water. I will do a full replacement of the gear oil this afternoon.

The prop is off, and I did a quick wipe-down of the housing. I will do a more thorough cleaning, and with the new oil, see what I end-up with.

Thanks again

 

[gewf631]

No Title

Looking like the suggestions were correct.

Lower unit oil came-out clean (no foaming, no water, no milky appearance), and was purple in color (I use Penzoil's lower unit oil).
The stuff on the floor was very oily (and there's a new puddle today), but black.

Soaked-up a sample of both on a white towel, and took a picture.

I really appreciate the help - once again, iBoats forum to the rescue!

Ed

 

[Chris1956]

Smell the stuff on the floor. If it stinks like your gear oil, you have a leak. If it smells like gasoline or oil, it is residual fuel..

 

[JoshuaFisher]

I have the same issue, without hijacking this thread what is the course of action to finding out why its not burning off properly as I have owned this boat for a year and it only recently started doing it... Thanks, and hope I'm not stepping on toes here but maybe we would both like the answer!