my tach is all over the place which is keeping me from tuning this engine correctly. sometimes at idle and w.o.t. it seems right but not all the time. i have replaced the rectifire with new o.e.m. but with no success. it is a faria tach which i replaced with another faria i purchased on ebay but still the same. it is pluged into control box with exception of gnd. wire which i ran direct to battery. i also to be sure i need to know correct # to set tach at. i shoud add the motor has a high speed miss just before w.o.t. that i can't seem to get rid of. thanks for any help as i prepare for boating season here in the north, i can't wait........