1974 Mercury 200 20hp ignition??

[Boater1010]

I just got a 1974 Mercury 200 20hp from my uncle and it has great compression at 120psi on both cylinders, but is not getting spark on the top cylinder. I have worked on many omc motors, but am not that familiar with Mercury ignition systems. It seems that they are more complicated as they have more components ie: stator high and low coil, switch boxes. Could anyone help me with some steps on troubleshooting the no spark on top cylinder? I would greatly appreciate any help. How common is it to have the stator or switch box go bad. I know these are expensive to replace. I am hoping it is a coil.

Thanks in advance.
Chris

 

[Gibbles]

Re: 1974 Mercury 200 20hp ignition??

Start by swapping the coils around, see if you have spark with the good known coil.

 

[Boater1010]

Re: 1974 Mercury 200 20hp ignition??

Hi
Thanks for the reply. I already fixed the spark issue. I narrowed it down to the switch box and replaced it. Strong spark now. This is a negative weak point on Mercury in my opinion and very expensive to replace.

 

[Gibbles]

Re: 1974 Mercury 200 20hp ignition??

Common issue with switch boxes, and they charge to much for them IMO....

glad you got it fixed

 

[skizur]

Re: 1974 Mercury 200 20hp ignition??

were is switch box location ihave same problem no spark

 

[Boater1010]

Re: 1974 Mercury 200 20hp ignition??

The switch box is on the left side of the motor if you are facing the front. Can't miss it. Its a black or silverish box about 2 1/2"x4" with about 7 wires coming out of it. Check the stator voltage at the terminals to the right. Hook up a voltage meter using alligator clips 2 to ground and red to terminal screw. pull the motor with the spark plugs out. watch the volt meter and make sure it spikes to around 120volt on both the brown and white wires coming from the stator. if you do not get the right or low voltage then you might need to pull the flywheel and check the stator.
good luck

 

[Boater1010]

Re: 1974 Mercury 200 20hp ignition??

do you get spark on atleast 1 cylinder or none? if none try to discconnect the kill switch button and make sure it is not grounding out. Also check all your ground for good connections and no freyed wires.