I'm trying to change the plug under the motor mount can anyone give me any advice on how to do this easily. Thank you

 

Sorry guy - In my experience with inboards - there is no "easy" way to do it. Because of the effort required to line up a new plug and get it seated properly - you're going to need some swinging room for your mallet. The "easiest" way to do it is going to be to put a hoist on the engine - raise it up enough to remove the engine mount to access the old plug.