Enlarging is easy... it's making it smaller that takes a little more timeI used those for my AC outlets. They are pretty good. Same price as the non dripless for that size, so that may be what I go with.
One thing I wave to do is make sure the shanks are the same diameter. I don't want to be enlarging or reducing the hole already in the boat. I should be a simple matter of removing the old one, cleaning up the hole and re-bedding the new.