O-ring at bottom of swivel tube/pin

[dvitatoe]

I have a bulging o-ring at the bottom of the swivel tube/pin (1999 Yamaha 225 saltwater series). It bulged out when I tried to add grease this past winter. How much disassembly is required to replace it. I can't even seem to get the lower engine mount bracket off to get to it. Does the lower unit have to come off?

[boats.net]

You will probably have to remove the swivel tube to replace the oring which means the powerhead will have to be removed to get to top motor mounts.