Like others have said, low voltage would account for all
your symptoms, and a professional mechanic would look
at that first. This is done not by changing parts until it runs
right, but by proper use of test equipment.
Attach a voltmeter, like an ordinary small VOA meter to the
"+" terminal on the ignition coil. If you have a separate
"ballast" resistor (as opposed to one inside the ignition coil)
then you will not see 12-14 volts there when the engine is running
right; the resistor should drop it to probably around 8-10 volts.
Anyways measure it when it's running good, then see what
is going on when it starts messing up.
Use the same technique to check the voltage at the input to
the instrument voltage regulator. That should of course be
12-14 volts.
My bet is the voltage is dropping substantially. But don't
assume it's the charging system. It could be in any one of
many places in your wiring. A poor connection someplace is
all it takes. A loose or corroded connection that is only a slight
electrical resistance when cold will become a high resistance
as it heats up from the current passing through it. To track this
kinid of thing down you need a wiring diagram and your VOA
meter. Check voltage at various places. Start right at the
battery terminals!
Carl Wade
retired marine repair shop owner
Williamson, New York State (near Lake Ontario)
B395000858 LRX
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