If the shaft and prop are insulated from the engine
nor bonded to any bonding system AND they both came from reputable manufacturers (so not an el cheapo prop) then I suspect you will be fine. Stainless steel
and bronzes (including the CORRECT grade of manganese bronze
which a good prop manufacturer will have used - manganese bronzes are actually brasses).
Our own prop and shaft were built purposely not needing anodes and has been fine for many years now. After the boat was built we lifted it several times over the first few months to check all was ok with that and other things and then again after around 9 months. So if the above applies regarding quality suppliers and insulation
then I would tend to just keep an eye on things, particularly the prop for dezincification.
If the prop and shaft are not insulated as above I would be the last person to give you any advice
without seeing the boat for myself and can only suggest that you find someone who has a good knowledge of corrosion
to look and give you advice
. Problem is it is probably easier to pull your shaft and replace it than it is to find someone who has reliable knowledge at a professional level. The electrical
engineers in a big yard building metal boats are usually the best but they are not easily accessible to most people.