After taking my boat (mercruiser 4.3 alpha 1 gen 2) out on the river i got back home and after cleaning it up noticed an oil leak from water pickup. Local mechanic says lower bearing is bad. he suggest i replace entire lower unit instead of attempting to repair Showed me slack/ wiggle in shaft and feels rough when turned. if you pull up on shaft and turn no wiggle and turning shaft is smooth. I have read this is normal on alpha 1 gen 2. Should I find another mechanic?