Got a all weld 20 ft boat. Flat bottom. Has had a lot of aluminum added to front. She's def heavy. Have a 1987 johnson 175 hp. Model is j175tlcua. Have about 14 inch by 24 pitch prop on it. Motor runs great. I can't get much over 4200 rpms out of it with some gear in boat. Had about 50 gallons of water in a tank this weekend. Brought down to 4,000 rpm. Thinking it's prop to steep and loaded motor hard. I wanted to check high speed ignition timing but says has to be at 5,000 rpm under load. Was curios if I could check the timing at high idle in driveway and disconnect the linkage that adjust timing and pull it to max and check it that way. Is there thing else electronically that adjust the timing besides throttle linkage that swings pickup forward?! Also, think it's pitched to deep?! Thanks.