I have 2005 merc opti 150. My problem is it used to run about 5500 rpm and bout 35-40 at wot. Now it sits around 4000 rpm and 25 at wot. I have changed fuel/water separator, cleaned plugs, and only use 90 not ethanol rec fuel with occasional sea foam. My alarm comes on and beeps for a few seconds then goes off and does this about every 20-30 minutes and the motor seems to stumble very slightly at higher rpm. Does anyone have a diy recommendation or is it time to break out the wallet for the marine mech?
