This is what we do..... Oil, filter, fuel filter, gear lube, remove the drive and check alignment, check all belts and hoses, power steering fluid, all bellows for proper attachment, check shift cable adjustment, motor mount nuts and lock tabs, etc. Basically we go over all the rigging to make sure nothing was missed or came loose and remove the oil and gear lube from breakin. We also do the sea water pump as many times that impeller has been in one position for a long time before it was installed in the boat and run.
I believe the 20 hour service is very important to long life and less failures in the future.