Tach goes to correct rpm as soon as engine starts. Only sometimes it will stick at that rpm after increasing the throttle to cruising speed (around 2000 rpm). After a few minutes it will usually move to correct rpm. 30 year old sailboat, 50 HP Perkins 4-108 motor. Any suggestions?
The ground wires should be serviced.
The ground from engine to battery
and altenator to engine block. Weak grounds will hinder current
flow and affect readings.