Mercury Trouble

I fished a tournament last Saturday and first blast off went fine as well as my second run. The next run was not as pretty, crawling up on plan and topping out 10 to 15 mph slower than usual. I am new to high performance bass boats and the boat and motor ( 2010 Bass Cat Pantera II, 2010 Mercury 200 Pro Xs) so Im still not sure what “right” feels like only owning the boat for 3 months. But there was a slight tick when idling making the motor shake every other second or so. Prior to all this I received a low oil warning on my smart craft gauges, so I checked that main tank and had about 2 gallons still present. Next I checked the small tank mounted on the side of the motor which was full. I assumed at that point that either my gauges needed to be recalibrate or whatever part reads my oil level needs repair. I called it a day and limped back to the ramp and added a gallon of oil and the alarm went away but still was mis-reading the oil level. I have now taken the boat to my mechanic and he said he would have to call Mercury tomorrow but the compressions where all at around 98 to 105 which he was not sure if that was normal. He thought it should be around 120. The only thing I have done differently was switch from Mercury opti oil to Mercury prem plus. Any ideas? Should I trust this wrench? I feel like I have a sick kid in the hospital!