1967 mercury 9.8 help

Bearskin9898

Seaman
Joined
Jun 19, 2018
Messages
59
Hey guys I have a 1967 mercury 9.8. The bottom unit oil leaks out around the prop so I'm sure my prop shaft seal is shot. I looked behind the prop and it looks like I'd also need to replace the bearing and I'm sure several other things too. I just spent $65 getting new fuel lines for this boat and for how old the motor is I'm really not willing to put much more money into it. I probably just keep filling it with gear lube hopefully it'll last at least a week at a time? So my question is, is there any cheap type of oil you can use to fill the lower unit with? Also what's the easiest and fastest way to fill it? Take the motor off the boat?
 

RCO

Petty Officer 1st Class
Joined
Jun 15, 2016
Messages
350
Are you sure it is gear oil leaking and not just unburned oil from the exhaust? If it smells like sulphur it is gear lube, if not it's unburned oil from the exhaust and totally normal. You can use regular automotive 80w-90 great oil in your lower unit, it is much less expensive than the stuff marketed as marine oil. No need to take the motor off the boat. You remove the small vent screw on the top of the lower unit, then fill from the larger drain/fill plug on the bottom until it comes out the vent screw hole.
 
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