Re: 1948 Evinrude Sportwin 4423 Revisited

[legendre]

Since it’s been brought up, here are a couple of comments on plug gap..

First thing to know, is that the plug gap determines – to a certain degree – the voltage of the spark. Think about it – the wider the gap, the greater the voltage required to jump that gap. So, for a given coil / magneto system, a wider plug gap forces the spark voltage to rise high enough to jump the gap.

Secondly, plug gap has a +significant+ influence over a motors’ tendency to be ‘cold blooded’.. wider gaps (if they can be reliably fired!) can and will reduce undesirable warm-up behaviors.

But once the gap becomes too wide, to the point that it can no longer be fired, then reliability truly suffers. Also, there are some cases where the (high) voltages developed by using a too-wide plug gap can injure the ignition coil, points or other components in the system.