Howdy! My 1979 mercury 80 HP that recently indicated 5200 rpm WOT @ 39 mph, now indicates 4500 rpm WOT @ 39 mph. It also recently started to quit running at random times. The battery starts the beast fine, I cruise for awhile to my next favorite fishing spot and in the process it may or may not quit. If it does, the battery is now dead. I connect a jump pack to it, start it up and it runs fine until the next time. If I shut the motor down as normal, it restarts with the battery like nothing ever happened except for the low tach indication. I have checked for shorted, chaffed, loose and broken wires and can find none. In concept, it appears the tach signal may be missing a pulse or two? Any assistance the experts can provide would be greatly appreciated. Thank you!
