I bought a 200 Opti 6 yrs ago for my Trophy 23. With the right prop, trolls fine 2.0 to 2.5 To go slower, trolling bags work great. I used two (to keep the boat from pulling to the side w/ the bag. Never had a plug fouling problem. Just run the boat @ 2500 rpm or better for 5 - 10 min when yer done to burn off the oil deposits. The 200 is a little noisy, but that's mostly from the compressors for the HPDFI. Also, I run it with front & side curtains on most of the time which captures the sound. It's not near as loud with bridge opened up.
Probably not quite as economical as a 4 stroke. I used about 0.5 - 0.7 gph at trolling speed. 18 gph at full throttle 5200 rpm and at cruise (3300 rpm) 5.6 - 6 gph. 17 mph. I've had the motor 6 yrs & have replaced the plugs once. Motor runs great. Last year I bought a 9.9 bigfoot long shaft on a Panther powwer bracket which I now use for trolling. It's quieter and uses even less of the expensive stuff. The dealer I bought the 200 from said to put in Merc Quickleenevery time i gas the boat. I have & it's all been great. Good luck!