Motor Marine - the stories I could tell you...
TBH, I don't know a decent marine mechanic in the county. There are a few who will do a reasonable standard service, but show them a faulty engine and the skills just aren't there.
If it's just overheating it should be something quite simple, a blockage, dodgy impeller or stat. It wouldn't be uncommon for an engine to go to MM for a service and leave with a bigger problem
Ronan Keyes can't be any worse.