here is one comment from an intelligent source....subject to approval..
flywheel
On your
1969 Evinrude 55 HP (model 55973A) you do
NOT have a steady “voltage feed” going to the points like on a simple automotive ignition.
That system is a
battery-powered CD ignition with breaker points acting as a trigger, so what you measure depends
how you measure it.
What you should expect on the wire going to the points (under the flywheel)
- Static / key ON / engine not cranking:
Typically little to no steady DC voltage (often near 0 V)
- While cranking (with a normal multimeter):
You may see only a few volts or erratic readings (this is misleading)
- Actual signal (with proper peak-reading/DVA meter):
A short pulse signal, not continuous voltage
Roughly 0.5 V to a few volts trigger pulse (points open/close event)
Key point (this is what trips people up)
- The points do NOT receive power to fire the coil
- They only trigger the amplifier (power pack)
- The amplifier then sends high voltage (~200–300 V pulses) to the ignition coil (you won’t see that at the points)
What voltage should be present elsewhere (for reference)
- Feed from key switch to amplifier:
about 12 V (must stay above ~9.5 V while cranking)
Practical diagnostic takeaway
If you're probing the wire going to the points:
- Seeing 0 V steady → normal
- Seeing low/erratic voltage → normal
- What matters is:
- Points open/close mechanically
- Wire not grounded accidentally
- Amplifier gets full battery voltage
Simple test (more useful than voltage reading)
Disconnect the points lead from the amplifier and:
- Tap it to ground while key ON
You should get spark each time it makes/breaks contact
(This simulates what the points do)
Q: so basically the wire to the breaker points is a "sense wire" checking for ground taps as the points open and close... tellingthe amplifier to fire the ignition coil
Yes — that’s exactly the right way to think about it.
On your
1969 Evinrude 55 HP, the breaker points wire is essentially a
trigger / sense line, not a power feed.
What it’s actually doing
- The wire from the points to the amplifier is:
Grounded when the points are closed
Open (no ground) when the points open
- The amplifier is “watching” that line:
- Closed (grounded) → it charges / prepares internally
- Open (points break contact) → it fires the ignition coil
In simple terms
You can picture it like this:
- Points closed = “hold” / charge
- Points open = “fire now”
So yes — it’s basically:
a ground-interrupt signal telling the amplifier exactly when to fire
Important nuance (worth knowing)
It’s not just “any ground tap” — the
timing of when the ground is removed (points opening) is what matters. That moment defines ignition timing.
Why your voltage readings seemed odd
Because:
- The wire is not supplying voltage
- It’s just switching between:
- ground (0 V)
- floating/open (which a meter can misread)
