Hi John and welcome to the heady world of model boating.
The connectors that fit between the shaft and the motor will overcome the problem as some of them are fitted with small grub screws that allow for adjustment and connection between dissimilar shafts.
The connector is a universal type joint such as you find on car prop shafts and a quick look at some web sites will give you lots of options.
I think its great that you are starting this hobby at 69 you will have all of the life experience and patience to get your models “just right”
Paul