George Benson
New Member
My 1999 340 Sundancer with twin Mercruiser 7.4s ran rough several weeks ago and then cut off completely (Starboard engine). The tach had jumped to 3000 from 1500 without the engine revving up. Checked compression/good, checked plugs/replaced, Distr cap/good, fuel filter/replaced, rotor/replaced, still running rough. Pointed out to the Mechanic that the tach would jump up significantly 1500-2000 RPMs without engine revving. He said "your tach is shorting out and that is what is causing the engine to rough". Is this right? How can something that measures something (RPMS) cause problems? The shop manual also indicates in the trouble shooting section that this can be a problem. Does anyone know why? :huh: