2 stroke to 4 stroke conversion help PLEASE

[trtdds]

I am thinking of upgrading my 1996 20' Champion Coastal Champ from it's original Mariner 200 HP 2 stroke to a new 4 stroke outboard. My boat is rated for 225 HP. Will I get the same performance with a 225 4 stroke as I get with my 200 2 stroke? If I need to get more HP to get the same performance, which of the manufacturers are using detuned 250's or 300's as their 225, and how hard is it to retune to higher HP? Which 4 strokes are best for salt water. Any help you can offer will be appreciated, as I am having trouble getting staight answers from dealers and manufacturers. Everyone I have talked to has told me there will be a decrease in performance, but no one has told me how much performance loss I will experience. Thanks for your help. If you have personally refit from a 2 stroke to a 4 stroke, PLEASE let me know about your experience.