Re: Merc 850 - Is it suppose to do this??
Before you go buying parts which is expensive,take a good look at your wiring.Wiring does get pretty brittle after so many years.You need more than 9 volts at the switchbox when cranking the motor or she will not start.I put in a new electrical wiring system to where my juice to the switchbox is on a seperate flip switch from the ignition key (starter). Here is a way of finding out if your switchbox and coil are in good shape.Also check your kill switch inside your control box is okay.
MERCURY BATTERY-POWERED CDI TEST FOR DISTRIBUTOR MODELS
This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.
This test assumes your coil is good (problems with CDI coils are rare).
DISCONNECT BATTERY
1. Turn off ignition;
2. Disconnect all 3 distributor wires on the Port side of the switchbox (and the ?mercury switch? if present);
3. Remove the High Voltage lead from the ign coil to the center of the dist. cap (remember it unplugs from the coil and unscrews from the cap);
4. Reconnect the H.V. lead to the COIL only;
5. Position the free end of the HV lead approx. 3/8" from ground (block, shrouds etc), and find a way to hold it there;
6. Jumper the brown and white terminals on the distributor side of the switchbox to each other.
RECONNECT BATTERY
7. Check that you have +12V at the red terminal (even with the ign off);
8. Turn on ignition and verify +12V at the white terminal (same side as the red terminal);
9. Ground the black terminal on the distributor side of the switchbox - this should cause a spark each time you touch ground.
If you get spark with the distributor bypassed, and it won't fire with the distributor connected, the trigger is bad and the entire distributor housing assy must be replaced.
If you get no spark using the test, the switchbox is probably bad. In that case, be sure to check for correct power on the switchbox, check all connections, and check the coil's resistance to make sure it's OK."
