In all the winterizing tips I see change lower unit lube.Mercruiser recommends annualy or every 100hr.Can someone tell me why? I understand the need to check for metal fragments and water intrusion but most autos and light trucks spend their whole life with the same lube and a lot of that time is spent hauling,towing,accelerating and climbing.I have not had a differential failure in 60yr and don't know anyone who has.What am I missing with OB & IOs? Just curious.
