I am a boating noob and I recently got a '93 bayliner classic, 16ft. It has a Mercury Force 70 and I'm having tach problems since I filled the gas tank recently. I filled it with a 50:1 gas oil mix. The motor sounds and pulls the same but the tach needle makes a big jump whenever I open the throttle more than a third of the way. The needle is not bouncing but rather making a full jump about 1/3rd of the way across the gauge (often into redline) until I back off the throttle, at which point it jumps back down 1/3rd of the gauge. I used to be able to go WOT without redlining. Have I made a mistake in my fuel mix or is there a problem with the tachometer?
