Upper and lower seals on 1975 25hp 'Rude

[jspringator]

When I got this motor off ebay last year, it had the most horrible lean sneeze upon starting; the motor wouldn't hardly run. Took it to a shop, and they fixed the loose slow speed jet that made the sneeze better, but it is still there occasionally. Cowling has evidence of oil shooting on it, and the motor and case were very dirty/oily. Sounds very loud and rough. Nothing at all like my super smooth 6. Plenty of power at full throttle. Lower throttle settings starting to do better with use. I haven't been able to use it too much because some days it won't start. I believe I have that traced to a sticking choke, which I have cleaned and lubed into oblivion.

How can I tell if the crankshaft seals are bad? I read the upper seals are prone to failure on the 18-20 25 series of 22 CID motors.