Here’s a safe way to remove and install spark plugs in those seemingly inaccessible places on marine engines. First, loosen all of the plugs with a socket. Then take an 18″ piece of 3/8″ or 1/2″ rubber fuel line and push it onto the plug, over the ceramic insulator. The hose grips it tightly enough that you can now unscrew the plug using the hose. The plug will stay in the hose, preventing you from dropping it into some tight spot. I also install plugs this way, inserting the new plug into the hose, aligning it and threading it into the cylinder head. The hose grips the plug tightly enough to allow me to thread it in, but not tightly enough to allow me to cross-thread it.
– Steve Abbott, Levittown, Pennsylvania