Check out the thread "2005 MC 197 help..." similar symptoms. I copy my friend's post below. Good luck!
"Thanks you all for the advice. After changing the in tank fuel filter, running 93 octane, knock sensor, water temp sensor, verifying transmission temp sensor for proper operation, and ruling out the oil pressure sensor, I was going over this with a friend and I asked, could it be a bad ECM? He said did you check the ECM ground? I put a 5/8 wrench on the 3 grounds on the bell housing. The one for the battery ground was good but the other two, that have grounds for the main harness, needed to be tightened. A couple of turns with the wrench and My problem went away! Lesson learned; I plan on checking these as part of my spring routine, to get my boat ready every year. I hope this post will help others. thanks again for the help"