dpsm outdrive holds pressure after seal repair but not vacuum.

[pae0332]

i have this drive from a 1998 v/p and the outer prop seals were leaking. i made the repair but it wont hold a vacuum of 15in, it drops to about 11 or 12. the book says to apply heavy oil to find the source.
has anyone done this that can walk me through it. i am not familiar with this process. .
thanks for any help

 

[alldodge]

15in of vacuum is a bunch, 5in is good enough

 

[Scott Danforth]

does it instantly drop? or slowly drop? what is it after an hour?

are you turning the shafts as you are testing?

if it slowly drops to the 11 or 12 overnight, thats fine. if it drops to zero, you sill have a seal leak.