That motor has Battery CD Ignition. (newer motors have Mag Cd ignition). The one you asked about has a sealed Pulse Pack, which contains the electronics. 12 V Power from the boat's battery is fed via the ignition switch to the pulse pack. The pulse pack increases that 12V to about 300V and stores it in a capacitor (the C in CD) until time to fire. A sensor under the flywheel detects when a 4-lobed rotor passes by. When it does that, it tells the pulse pack it is time to fire, and the pulse pack discharges (the D in CD) that 300V stored in the capacitor to an externally mounted ignition coil. The ignition coil is a type of transformer that increases the 300V to whatever it takes to fire the spark plug (thousands of volts). But wait, before it can fire the spark plug it needs to know which plug to send it to. That is done by a distributor, also under the flywheel. That is similar to an automotive distributor. One other thing under the flywheel is a reverse cut-off spring, made of silver wire. That disables the ignition if the motor tries to run backwards. Yes it is possible for it to run backwards.
EDIT: You ask if it is a decent engine. Well, that Battery CD system was state of the art in 1970. But the Mag CD introduced in 1973 is way far superior, and still used today. The Hydro-Electric Shift on the 1970 was a good unit but proper maintenance is a must. And the shift switch in the remote control costs a small fortune, IF you can even find one.
