79 mercury 90hp 900 no spark

talbee

Seaman
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Jul 26, 2015
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I have replaced new parts: switchbox, solenoid, starter, rectifier, and plugs.

The motor wants to turn over, but when I try to link and sync there's no spark.
 

racerone

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Tested stator and trigger unit ??------Is the starter in good shape and turning the motor fast enough ?
 

talbee

Seaman
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Jul 26, 2015
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The starter turns the motor fast enough. I thought about testing the other 2 you've mentioned, but Idk how or have the tools.
 

Faztbullet

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You stated you replaced switchbox, do you have a distributer or twin switchboxes and 6 coils???
 

Faztbullet

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Your motor is a 1977 or early 1978...Disconnect mercury switch from trigger wiring....
 

Chris1956

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Also, you must have +12VDC on the red wire on the switchbox, and the adjacent white wire on the switchbox, when the ign key is in the start and run positions..
 

jimmbo

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May 24, 2004
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Possible problem in the control box, as in bad ignition switch or wiring
 

talbee

Seaman
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Jul 26, 2015
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So sorry for the delayed response. I ran voltage checks on everything I could think of and voltage is good. Jumped the distributor to check for spark on the coil, getting spark. Still no spark on the first plug when trying to lync and sync.

The only other thing I could think of now is the stator. Thoughts anyone?
 

Faztbullet

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1) Do you have spark on the plugs when cranking over? 2 )If you only have spark by jumping distributer the trigger is bad 3) the stator has no effect on this ignition system as it only charges battery.
 

talbee

Seaman
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Jul 26, 2015
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Is there anything else I could check before I make a final determination to buy the trigger? I was thinking the little box under the distributor where the center coil wire attaches to. Is that call the ignition box?
 
Last edited:

Faztbullet

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Mar 2, 2008
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  1. Connect a spark gap tester to the high-tension lead coming from the ignition coil and set it to approximately 7/16". When you crank the engine over, if it fires while the spark gap tester is connected to the coil and does not fire through the spark plug wires - there is a problem in the distributor cap, rotor button or spark plug wires.
  2. Check the DC voltage present on the white and red terminals while at cranking. It MUST be at least 9? volts. If not, there is a problem in the harness, key switch, starter, battery cables or battery.
  3. Check the DC voltage on the brown trigger terminal at cranking, there must be at least 9V available with the trigger wire connected.
  4. Check DVA voltage between the white and black trigger wires (They must be connected to the switch box). You should read at least 3V. A low reading indicates a bad trigger.
  5. Align the rotor with #1 spark plug wire. Disconnect the trigger wires and connect a jumper wire from the white trigger terminal to the brown trigger terminal on the switch box.
  6. Connect another jumper wire to the black trigger terminal turn the ignition switch on. Strike the jumper wire from the black terminal against engine ground ? (DO NO HOLD THE JUMPER AGAINST ENGINE GROUND!). Only the #1 spark plug wire should fire.
  7. If unit fires when tapped to ground switchbox is good and trigger is defective.
 

talbee

Seaman
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Jul 26, 2015
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Thank you everyone for the responses. I'll double check everything again then get back on here if there are further issues.
 

talbee

Seaman
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Jul 26, 2015
Messages
62
After removing the distributor and cap and cleaning them, the motor started. Yesterday I tried to start it, but got nothing. I checked for spark, but there's no spark again.

I was looking at the wires coming off the stator and noticed they're a little shotty. Would that have anything do with no spark as well?
 

talbee

Seaman
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Jul 26, 2015
Messages
62
Motor started. Next day it didn't start. I checked for spark and got nothing. Took the stator off and checked the ohms and ohms read according to specs. Put stator back on and still no spark.

Is there anything else I should check before dropping $300 on a distributor/trigger?
 

Chris1956

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Mar 25, 2004
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Stator had no effect on that motor. It only serves (with rectifier) to charge the battery. Triggers can give spark one day and not the next. Triggers are part of the distributor housing, and must be replaced as an assembly. Save your pennies, nickles and lots of dimes.
 
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