It sounds more like excessive play in the coupling/shaft connection and nowt to do with the prop.Engine is very poorly and out of the boat.
Cleaning out the empty space today I casually twirled the coupling. Seems like there is a couple of degrees play in both directions before the prop turns.
Is the prop loose on the shaft, and if so why? Don't want to add a Cascais liftout to the cost of fixing the engine. (Plan is to have a wee sail around the Algarve then lift out at Bruce's if there is space, so will fix wonky props etc then, but will it fall off before then?)