Max-Props should be greased once a year. This can be done in or out of the water. If the boat is in the water year round you should have a diver in the water at least once a year check anodes; they can grease the propeller at that time. Or, if the boat is hauled every year, it is easy to grease it while it is out of the water.
Max-props recommend to use Lubriplate No. 130-AA grease. This product is designed for those applications where a grease-type lubricant possessing extremely good water repellency and superior lubrication characteristics are desired. These products are recommended for plain bearings, cams, guides, open gears, slides and chassis lubrication and where temperatures do not exceed 76 °C.