OTOH my wag right now is it froze over the winter and water seeps into the engine when it sits.
Or it could be something totally different
The basic issue is the OP is not enjoying his boat. This is not his job, it is hobby and he seems to have not realized what owning a cruising sailboat entails.
* this reminds me of a friend with a Model A Ford. He quickly learned that if he wanted a reliable car to drive, he either needed to learn to work on it or get a new car because the local shops were not good with cars from 1930 and he couldn't afford the time or money to get the car to a specialist shop that knew the car.