1985 70 HP Yamaha - misfires at high speed

[gnibbe12]

This problem developed recenty - Engine runs fine up to about 4500 rpm. Above this speed, the yellow low-oil level warning lamp starts to flicker on/off (green lamp stays on steady as it should) and if the lights are turned on I notice they glow bright during the flicker - and -the engine runs rough as if there is intermittant spark. I am thinking there is too much voltage output from the lighting coil at high speeds and/or it interferes with spark-ignition coil. Or maybe a bad voltage regulator. When the flicker starts I sometimes get an electrical shock at my hand holding the stainless steel steering wheel (while my other hand holds the throttle/shift lever). As long as I don't run at high speed, everything is normal. Any suggestions ?