If you look along the shaft towards the shaft opening you will see tiny ridges of rubber around the shaft where it penetrates the hull. Now gently scrape away the anti fouling along the side of the hull moulding where the shaft exits and you will see either one or more likely two tiny hexagon grub screws.
Remove these.
Disconnect the shaft inside, remove the drive flange ready to withdraw the shaft.
Lubricate the part of the shaft inside the boat with a strong soapy water mixture to aid withdrawal and do the same when refitting.
Remove the shaft.
Now you will be able to see inside the aperture either a brass or phenolic tube with a small coating of ridged rubber inside, that's the cutlass bearing.
Take a drift slightly smaller than the tube and gently drift it out, be sure to keep the drift 'square on'.
After the cutlass bearing is removed measure the inside, outside, diameter and length and re order a new one.
My tip would be to replace the old stuffing box with a PSS seal, far superior with virtually no maintenance other than periodic checking.
While the shaft is out get it checked for straightness and balance in a hydraulic ram repair shop and get your propeller checked for any repairs or balance.
Refit in reverse order with a light coating of copperslip (non seize grease compound) on mating metal surfaces.
When finally connecting the drive flange to the engine make absolutely certain sure the engine/shaft alignment is nothing less than perfect.
Near enough simply isn't good enough.
I would check engine mountings and the clutch drive plate while everything is stripped out.
The extra effort you put in now be well rewarded with many years of trouble free cruising.
I hope this is helpful to you.