1991 150B force outboard no spark

Nordin

Commander
Joined
Jun 12, 2010
Messages
2,638
Do you have Prestolite ignition system with three blue or black CD modules?
Or do you have Mercury Thunderbolt system with one switch box?
Normally the CD modules or switch boxes can not be tested from resistance with a VOM.
You test for voltage from the stator and triggers to the CD module/switch box and output voltage from the module/box to the ignition coils.
When testing you need a DVA adapter connected to the VOM/multimeter or a multimeter with DVA function.
If no spark at all five cylinders it looks like the stator is bad as it charge the capacitors in the modules/box and if you have Prestolite system and no spark at all it is unlikely all CD modules goes bad at the same time.
Outboardignitiondotcom has the troubleshoot chart for these systems.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,122
Linc to Outboardignition.com and CDI
Test and repair/sales




Unit will not fire: 1. Disconnect kill wire AT THE PACK. 2. Check for broken or bare wires on the switch box, converter and trigger. 3. Check the DVA voltage of the converter, (Read from the blue wire to engine ground), with everything connected. The readings should be approximately 180 volts or more on the blue wire, and 11.5 volts or more on the red wire to engine ground. Engine will not kill: Check kill circuit in the pack by using a jumper wire connected to the black/yellow wire coming out of the pack and shorting it to ground. If this kills the engine, the kill circuit in the harness or on the boat is bad, possibly the ignition switch. High speed miss: Check DVA voltage on the blue wire to engine ground at high speed. NOTICE: Use caution when doing this and do not exceed the rated voltage range of your meter. The reading should show a smooth climb in voltage. If there is a sudden or fast drop in voltage right before the miss becomes apparent, the converter is usually at fault. If there is no indication of the problem, it could be mechanical problem. Coils fire with spark plugs out but not in: Check for dragging starter or low battery causing slow cranking speed and low voltage to the Converter. DVA test Converter and trigger. Intermittent firing on one or more cylinders: 1. Check for low voltage from the converter and trigger. 2. Dismount the ignition coils and inspect the coils for cracks and broken ferrite cores. 3. Using the connection legend, swap the problem trigger wire input to the switchbox and the associated output wire to see if the problem moves to the other cylinder. If it does, the switchbox is likely bad. If it stays on the same cylinder, the trigger is likely bad. CONNECTION LEGEND Cylinder # Coil Color Trigger Color 1 Green Brown 2 Green/White White 3 Green/Red Violet 4 Green/Black Black 5 Green/Yellow Yellow All cylinders fire but the engine will not crank and run: Index the flywheel and check timing on all individual cylinders. If the timing varies, replace the switch box. Timing Advanced: Using an ohmmeter, check the resistance on the White/Black wire from the switch box to engine ground. You should read approximately 8.5K ohms. Readings below 8K ohms or above 9K ohms indicate a bad switch box. Switch Boxes Blows Repeatedly after a Short Running Time: 1. Dismount the ignition coils and inspect the coils for cracks and broken ferrite cores. 2. Connect a DC volt meter from engine ground to the kill wire from the engine harness and turn the key switch on and off several times, AT NO TIME SHOULD YOU SEE ABOVE .8 VOLTS. A reading above 0.8 volts indicates a problem in the keyswitch or harness.
 

Tim Collie

Cadet
Joined
Mar 31, 2022
Messages
8
Do you have Prestolite ignition system with three blue or black CD modules?
Or do you have Mercury Thunderbolt system with one switch box?
Normally the CD modules or switch boxes can not be tested from resistance with a VOM.
You test for voltage from the stator and triggers to the CD module/switch box and output voltage from the module/box to the ignition coils.
When testing you need a DVA adapter connected to the VOM/multimeter or a multimeter with DVA function.
If no spark at all five cylinders it looks like the stator is bad as it charge the capacitors in the modules/box and if you have Prestolite system and no spark at all it is unlikely all CD modules goes bad at the same time.
Outboardignitiondotcom has the troubleshoot chart for these systems.
I have the thunderbolt system if the switch box has failed this will be the 3rd in 20 yrs
 
Top