I recently bought a 1975 Bristol 27. We motored it from Chicago to Milwaukee (about two 10 hour days). At the end of the first day the motor stalled a few times trying to get into gear, and smoked a bit. I have been dealing with a leaky head, and a lot of unknown rigging. So, yesterday we motored out of our mooring and after a few minutes the motor revs started oscillating. I turned quickly and went back to the mooring. Now after the worry of moving an unknown boat a long way, and dealing with a bunch of other new-old boat things, I am at a point that I don't have any confidence in the boat.
Have you ever felt like you can't trust your boat, and it scarred the crap out of you?
Welcome to the world of yacht ownership. Unfortunately, it seems that nearly every buyer of an older boat discovers some issue or another ex post facto and feels some disappointment, frustration and uncertainty. It goes with the territory, at least initially. You bought the boat but don't yet "own" it (although some might say it now own's you!).
In re your engine, I suspect 90% of engine problems are fuel related. EIther contaminated fuel itself because of water and gunk in the tank--which get's churned up when on a long trip and fouls the fuel filters; or a defective fuel delivery system. If you are not yet a good mechanic (you will become one if you keep the boat for very long and are not a wealthy dillitant), hire a good one to help you, at least initially, and learn from him/her. Cleaning/replacing filters, getting fuel polished and tanks cleaned, and even replaceing fuel pumps and lines and bleading systems isn't too complicated although, sometimes, a pain it the butt.
Likewise, if the head leaks, they really aren't that complicated and can be rebuilt pretty easily although some contortions may be necessary (and your 4-letter word vocabulary may be expanded in the process!).
Rigging is another matter and I suggest you leave that to a good rigger. The good news is that, given the size of the yacht, even if you have to replace all of the wire, it won't set you back all that much (although likely more than you counted on when you go into the process).
Despite the misgivings and initial frustrations and disappointments, if you stick with it, at some point you will find yourself anchored in some cove--maybe in Door County--enjoying a glass or cup of your favorite beverage and marveling at how fortunate you are. Then you will own your yacht.
PS: Matt's suggestion for a BoatUS Policy of towing insurance, above, is a good one--just in case.