Bayliner Boat 2003 - Needs New Engine

We have owed this boat for 5 years now and have had a lot of family fun with it. It's an excellent boat for water skiing, knee boarding, fishing and just general pleasure on the water. For the time that we have owned it we have kept if on a fresh water lake in France.However, the last time we used it the engine started to loose power and splutter, so we had a boat mechanic look at the engine in France. He told us it needed a new engine which seemed a bit unrealistic so we picked it up and now store the boat at our property here in Surrey, UK. I personally think that a good mechanic would be able to repair the engine, but failing that it would need a new replacement.
All the engine parts are with the boat but it is not assembled.The trailer is in excellent condition and very sturdy. The boat tows really well.The boat also comes with a full bimini that when fitted to the boat completely encloses the cabin area. There are 8 upholstered seats all in excellent condition.There is also a travel cover that is in really good condition (1 popper missing) and a rain cover that is a bit ripped on the back and could do with some repair.The rest of the boat in terms of steering, prop, dashboard etc are all in perfect working order.