I have a 1978 115 hp Merc that seems to run fine, but I'm not getting optimum speed. It starts fine, idles fine, WOT rpm is 5500. I checked compression and it's low but even. I'm new to this so maybe I screwed that up, I checked compression cold-should i do this while motor is warm? When I decarb I can bog down the motor with each carb so I assumed I had spark on all 6, is this a wrong assumtion? Should I check spark and what is the best troubleshooting method for this?