Just consider this: Oil is put in there to prevent friction between two moving parts. The spring clutch consists of a spring which is attracted to the clutch hub when the hub is electrically magnetized. The attracted spring then grabs onto the hub, locking them together and driving the boat. This action depends on friction so they lock up tight and don't slip. The engineers realized that and specified oil of specific friction preventing qualities. It must prevent friction wear, and at the same time allow enough friction so the clutch can lock up. BTW, a similar situation exists in automatic transmissions where clutches are submerged in oil. Thus the related oil qualities. So, to answer your question, yes wrong oil can cause clutch slippage and resulting wear. So can dirty oil, the dirt modifying the friction qualities.