My charles industries 40amp charger is starting to act up. I may need to change it, but they apparently no longer manufacture marine chargers.

Would you think a 30 amp charger or even a 20 Amp would be sufficient?
We run generators 100% of the time aboard and only use my 24v bank ( that supply house and engine start) for the vacuflush systems and a few other minor accessories. I’d like the charger to handle starting the engines from a weak bank if need be.
My setup is 2 pairs of 8D batteries per Detroit diesel supplying some house and starting of main engines.
( my 12v generator bank is separate and run other shower pumps and minor lighting etc)

I’ve never seen my charger at 20 amps on the gauge in all my years with regular usage.