nb Innisfree

For the record I found tightening those two locknuts backed off the bolts from the shaft and therefore loosened their grip, better to remove locknuts and use threadlock on the bolt thread. I actually replaced bolts with Allen grubscrews.

I've only caught it once, felt it sliding slowly upwards, closing paddles would have taken too long so instead I put full forward revs on and waggled the tiller like mad, a controlled panic if you like, did the job, phew!

Yes I agree, it would require removal of four bolts, not nuts. Removal wouldn't be necessary, just slacken them off to their full length

Innisfree had that type of top bearing, quite common. The two lower nuts position the plate which is welded to lower half of bearing holder, removing the four bolts allows top half of holder to be lifted off, then plastic bearing can be replaced (after swan neck is removed of course) ETA: Bearing is spherical to accommodate various angles of rudder shaft.

I once lifted a rudder back into place for a boater, he was amazed, in 27 years of boating he'd never come across such a thing!

The heat from a small pet would prob suffice, a mouse perhaps.

Instead of a bilge blower you could use a Ecofan positioned over a candle, make sure it's a very small candle or the power generated could blow your windows out, maybe an emergency snuffing arrangement just it case.