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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14306
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Mercury 700 (70 HP) no spark, it would run good then lose spark

Customer Question

mercury 700 (70 HP) no spark, it would run good then lose spark once shut off. now no spark at all, would it be the coils, switch box or stator
Submitted: 8 months ago.
Category: Boat
Expert:  Jason replied 8 months ago.
Hello my name is ***** ***** am I speaking with? All Mercurys are cataloged by serial number, do you happen to have your serial number handy so I can run it and see exactly which ignition system you have on that engine, and pull specs.
Customer: replied 8 months ago.
Hi, my name is*****(###) ###-####
Expert:  Jason replied 8 months ago.
Hi Scottie, unfortunately that's not pulling up, likely because the age of it.Is this a 3 or a 4 cylinder engine?
Customer: replied 8 months ago.
3 cylinder, it does have the thunderbolt ingnition system on it
Expert:  Jason replied 8 months ago.
Got it. I do have the instructions for troubleshooting this ignition system. It will require a decent quality digital volt ohm meter, which is something I don't know if you have or not. And it will also require an adaptor called a DVA for said multi meter. Was this something you were looking to troubleshoot yourself?
Expert:  Jason replied 8 months ago.
Here is how to troubleshoot this ignition system. 1. If a mercury tilt switch is connected to the switch box, disconnect it and retest. If you now have spark, replace or discard the mercury tilt switch. 2. Check DC voltage on the White and Red terminals (White wire on the(###) ###-#### (they must be connected to the switch box) to Engine Ground AT CRANKING. It MUST be at least 9.5 volts. If not, there is most likely a problem in the battery. Try a known-good non-maintenance-free cranking battery. If no change, check the key switch, starter and battery cables. 3. Perform the jumper wire test in the illustration above. Disconnect the trigger wires from the switch box and connect a jumper wire from the Black trigger terminal/wire of the switch box to the White/Black trigger terminal/wire of the switch box. Connect another jumper wire to the Blue trigger terminal/wire of the switch box. Turn the ignition switch to ON. Strike the jumper wire from the Blue trigger terminal/wire against Engine Ground – (DO NOT HOLD THE JUMPER AGAINST ENGINE GROUND). The ignition coil should spark each time the Blue wire is tapped to Engine Ground. If not, the switch box and/or ignition coil is faulty. 4. 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 sparks while the spark gap tester is connected to the coil and does not spark through the spark plug wires – there is a problem in the distributor cap, rotor button or spark plug wires. 5. Check DC voltage on the White/Black trigger terminal/wire (it must be connected to the switch box) to Engine Ground ATCRANKING. It must be at least at least 9V DC. A low reading indicates a bad switch box. 6. Check DVA voltage between the Blue and Black trigger terminals/wires (they must be connected to the switch box) AT CRANKING. It must be at least 3V DVA. A low reading indicates a bad trigger. 7. Check DVA voltage on the Green wire going to the coil to Engine Ground AT CRANKING. It must be at least 100V DVA. A low reading indicates a bad switch box. That is how to do it. Do you have any further questions on the issue?
Customer: replied 8 months ago.
ok, i have to tools to test this, i will let you know my findings
Expert:  Jason replied 8 months ago.
A DVA isn't something you would have unless you were either an outboard, or a motorcycle mechanic that works on magneto driven ignition system. If you need a recommendation as to where to get that tool just let me know and I can point you towards a couple of suppliers.
Customer: replied 8 months ago.
ok, i have tested everything that i can with my volt ohm meter and resistance tester, everything has tested normal, i did notice that i have a frayed wire that comes from the trigger, it was on the very top left of the switch box. i replaced the wire and did manage to get spark from the coils, but the spark only happened sometimes. so does that mean i have a bad trigger, or coil? where would be the best place to get a DVA tester?
Expert:  Jason replied 8 months ago.
What you would need to do is measure the voltage out of the trigger and stator with the DVA. If those voltage are low, then replace those parts. If they are good, then that points to a bad switchbox. On the DVA, I have one from Snap on that fits my Fluke meter and works great. Click these links below, these are all places you can get a DVA from. https://store.snapon.com/Multimeter-Accessories-Adaptor-Direct-Voltage-P649400.aspx http://www.amazon.com/CDI-Electronics-Voltage-Adapter-511-9773/dp/B001O4TZGG http://www.stevensinstrument.com/peak_dva.htm
Customer: replied 8 months ago.
My neighbor has a 1978 115 mercury, do you know of I can just can change all of the ignition system out with that one?
Expert:  Jason replied 8 months ago.
His 115 is more than likely a 6 cylinder, and a completely different engine.
Expert:  Jason replied 8 months ago.
Hi Scottie, just checking in, how are we making out?
Customer: replied 8 months ago.
Still waiting on my dva tester to come it. I did however get it to start by removing the white\black trigger wire, so I'm thinking I will need a new trigger
Expert:  Jason replied 8 months ago.
It very well may be the trigger, once you check the voltage output you will know for sure.I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.Thank youJason

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