We have many "mechanics" here who say and apparently honestly believe that they are competent to work on particular engines, but it's too often just not true. And several of the ones I know (I've owned five working boats here) are well capable of creating work for themselves. For example, I used to have to replace control cables quite frequently, till I discovered that the mechanic was fitting ones a little too short, so the curves were too tight. And another one removed all the sacrificial zinc and didn't replace it.
If you can provide a sound and well informed service then you will be able to operate here. Don't expect to earn a lot though.