Be gentle, but it's probably time to blow off your mower. After all, your trusty steed, whether it's a push or riding model, gives you a nice, big beautiful lawn. Don't you want your equipment to look as good as that? When those grass clippings cling stubbornly to that shiny metal, it can be pretty ugly. Even worse after they dry.
Use your leaf blower to get rid of the unsightly mess that mars the beauty of your mower. It's much easier than trying to hose it down and won't get anything waterlogged, either. Just don't aim it at the neighbor's yard - and for goodness sake, don't clog up those city drains.