You will find that mobile services liaise very closely with Yamaha dealers as they need to get their parts somewhere, they use tanks and not earmuffs and have the same diagnostic software and a large store of parts. I use a local mobile mechanic and he is extremely thorough, has all the latest bulletins etc. My closest dealer is 30 mins away but nearly everyone who has used them finds their aftersales service atrocious, I will travel another hour further if needed to Stones Corner Marine, they too are awesome. I am not sure but how many dealer mechanics would be factory trained. My non dealer mechanic is not any cheaper but he checks absolutely everything and is very convenient. Arguments like these only serve to perpetuate urban myths.