Manufacturers will have different recommendations as to when to change your oil filter; however, it is advisable to invest in a new filter every time you change your oil. If your oil filter mounts vertically, it should be fairly simple to replace. For oil filters that are bewilderingly mounted horizontally or upside down, you will need to have a bag ready to contain the outboard motor oil that will inevitably spill during the removal process.
The vast majority of oil filers spin-on, which means that you will need a strap wrench to remove them. Before putting the new oil filter into place, coat the gasket with oil. Screw the filter in by hand, ensuring that the gasket makes full contact, and then tighten it another three-quarter turn. For older boats, there is typically a center bolt that must be removed before you can access the cartridge oil filter.