TOPIC: Tachometer

I need a tach, nothing outlandishly expensive for my '61 Royal Scott. Anyone knows off the top of their heads the number of poles.....I really don't want to pull the flywheel and count magnets. I assume it is a alternator since it has a stator and a rectifier. Would like to know rpms for setting idle and this weekend for the maiden voyage to see just what is happening.