Hope you didn't pay much for the winterization if that's all he did.
You'll want to see if he did any of the suggested maintenance when he did this work which I doubt. With a new to you boat the first thing I would change would be the impeller. Going though the engine checking hose clamps, belts and obstructions in the transmission cooler would be the next items on my list. Finish that off with greasing the fittings on the steering cable, shift cable and transmission linkage should get you in pretty good shape.