Hey all! Quick background, I’m the new owner of an old boat… I recently acquired a 1987 Lund with a 135 Mercury oil injected 6 cylinder 2 stroke that my dad bought new. I’ve grown up in the boat and always remember dad complaining about the boat being cold blooded, but I always ran around in it with no major issues sticking out in my mind. Well, fast forward and the boat has spent the last 5 years sitting on dry land (dad had it all gone over by a mechanic, used it once and then winterized it and never used it again). I inherited it this spring to use it as a family fishing boat. We got it running relatively easily on the old gas (have since ran 3-4+ tanks of 91 non-oxy w/Sea Foam through it including one time running it bone dry). In the process of trying to get it running right I’ve replaced the stator, plugs, water pump, and a few oil injection lines. I recently decarbed it as well. Checking the spark it looks strong across the board. Ohms tested the coils and they checked out. It’s running OK at true idle, starts relatively easy, decent top end, but the issue is that occasionally it coughs and dies while idling around in no wake zones. It doesn’t happen 100% or the time, but fairly frequently and usually around 900-1,200 RPMs seem to be the bad spees. At times when running slowly around the docks or gradually accelerating it seems like I’ve got a cylinder or two dropping out? 2 of the plugs look cleaner than the others when I check them. Also, when I’m running wide open the engine temp gets 3/4 of the way up the gauge, but cools down promptly when slowing down. I don’t know where head next… Any input is greatly appreciated. In a perfect world I’d repower with a new 4 stroke but not in the cards right now. This boat has a lot of sentimental meaning to me as it was my dad’s pride and joy when I was young but currently my wife is currently getting frustrated with it and me for spending too much time and money on it 
Thanks in advance for any help!!!
Thanks in advance for any help!!!