This is not un-common. I hear a lot of these type problems occuring and feel bad, that there is no law or anything anyone can do to stop it.
The best protection in preventing this type workmanship, is to arm yourself with knowledge before you go to a shop. The second best thing to do, is make sure the mechanic is a OEM certified Rotax mechanic.
I take in skis at my house regularly, to help repair. I got a real job and raise two kids. I do this for my neighborhood kids, who can't afford $90 bucks an hour for a shop. Everyone I deal with, knows the extent of my knowledge. I will tell them if I can't fix it. I will tell them I'm not sure what it is, but I'll look into it....etc.....but you won't find this kind of honesty in the boat repair shop. Why?
Because they know we are at their mercy. There are a lot of car repair shops, so there is a lot of competition. They know, that if they do a good job, they'll get you back as a repeat customer. The boat world is completely different. There aren't as many boat shops, they have a back log of customers for a couple months back and could care less if they screw your stuff up or not. They got your money and if you don't come back, so what!....they got the next joker in line waiting to pay them for the same kind of messed up job. They never go broke.........:rant:
Sorry for going on and on.........but I'm very pessimistic about boat repair shops.