mystery oil

[josh_booth]

Was thinking about going out for the third trip this weekend. Changed from my 19P prop to my 17P, when I got the 19 off there was a small amount of oil behind the prop, not even an ounce. Changed impellor and out drive oil before the season. Checked outdrive oil today and it's still full. The seal looks good and doesn't appear to be leaking, any ideas on how or where to look for where the oil came from?

Edit to add it's a 76 MC-1 outdrive behind a 120 Mercruiser

 

[alldodge]

A seal is leaking and the most probable one is the prop shaft seal. Will it leak enough to cause an issue, probably, but don't know for sure. If you drain the lube and pressure/vacuum test it you should be able to find which seal is leaking

 

[Scott06]

Check the drain screw as well to make sure no water is getting in, will be water or milky is seal is leaking. I had a similar experince with an old mc1 saw some oil sheen, was full, drive worked until lower gearcase was 1/3 water, then the drive died