“No Spark” Is it a Bad Switch Box, Stator or Trigger? Using a DVA Adapter - 1989 45 hp Mercury

This 45 hp Mercury lost spark on all four cylinders. The owner wants it fixed and asked me to diagnose the problem and fix it. Is the Stator, Trigger, Switch Box or Coils?

This video is how I diagnose which component(s) failed to determine what it needs to get it running again using just a volt/ohm meter and a Direct Voltage Adaptor (DVA) . The ohm meter is used to measure resistance for the Stator and Trigger then finally using the DVA adapter being plugged into the Volt Meter measures peak voltage. This is needed because the volt meter by itself measures only average voltage, whereas the DVA is needed to measure peak voltage outputs.

Part 2 - “New Switchbox Regained Spark Now Overheating - Find out Why”:
Part 3 - Carb Clean & Install
Part 4 - Still to Hot
Part 5 - Overheating? Try This!
Part 6- Overheating - Found the Problem & Resulting Carnage.

[jamesnottingham]

was watching your video. My 85 hp Yamaha would not fire. When you checked the kill switch, I remembered i had broke my kill switch wire when the seat fell on it. I hooked kill switch up. engine started. :)

[unsaltedlife]

Very nice walk through, I’ve seen people just start buying parts and never walk through the check list and it cost them so much money before they figure it out.

[alafanlaman]

Great video. For me, it was blue to blue/white on stator. Would crank cold, but when warmed up, would not crank. Would get an ohms resistance reading intermittantly on blue to blue/white. Found this article online for an explanation of why this could happen. I am no expert, but it makes sense. It's like ghosts living in your engine.

From an old post in 2007.
One more thought with regards to the dual winding on a Mercury stator. It would make sense to me also that the main purpose was to give a better, higher amperage charge at lower RPM.
However, when reading posts on a Mercury outboard specific site, one of the first indications of a problem with the lower speed winding is weak spark when cold, but enough that the motor will start. Of course, the motor started so, like me, you'd go off on your merry way and forget about it taking a few more cranks than usual. Once the throttle is down and the RPM increases you've unknowingly switched to the high winding on the stator. Your second clue to a bad low speed side is when the motor is now warm, and you shut it off. The malfunctioning low speed winding is now also warm and has become an open circuit, so the motor won't restart. Sometimes, as in my case, the circuit closes when it cools, allowing the motor to start once again, but giving you an intermittent issue that is by nature hard to diagnose. I got this clue about three times, but was too bull headed to investigate before it finally quit altogether.

So, while I'm sure the low speed winding helps with low RPM charging, it apparently also has the primary role in supplying spark to the motor.

jandrewg posted 05-23-2007 11:47 AM ET (US) Profile for jandrewg Send Email to jandrewg

[ricksnowden]

Watching this, I found myself wanting to be the other hand you needed. GREAT VID, VERY HELPFUL.

[TheBestYouthWrestlingVideos]

The screenshots I've taken from your videos of how this all goes back together are priceless. Thank you good sir🙏🔥

[cylon]

This helped me out alot. I've a 78 50hp merc with the 4 wire stator. Read all pairs good skipped the dva voltages and went directly to cranking voltage reads, found a black box in between the stator and switchbox that read open, so i bypassed it. Couldn't find a drawing or part number on the net. Started right up.
Thank you so much for clear concise information.

[markmorgan]

Thank You. My switch box and stator were both bad. Sparking like crazy now :)

[MitzvosGolem]

I worked on these since 1970s up until 1990s Salt water corrosion nightmare.
Often had power pack low speed charge coils went bad when hot.
Sone older Mercury had a tilt kill switch with mercury liquid in them hooked to kill wire and a dead man switch in control by box .
The older 6 cylinder had distributor cap with trigger and a belt.

I have a 1990 Yamaha 50 all original electrical ignition .

Nice channel 👍 Thanks

[MrJmattr]

Great work! Just went through this on a Mariner 80. Same readings that you had. Time for a new switch box.

[dominikzaleski]

This helped, a lot! Thanks for not skipping the small stuff!!

[TonyClemmons-gp]

I just did all this. My black wire on the trigger didnt make any volts while cranking I’m assuming it’s bad. Very helpful video sir

[agmcme]

excellent video, I have a customers 8 hp that drops a cylinder but will come back with a little rev of the throttle, I need to do all theses tests.

[littletoze]

If you get a chance, or even want to, I got this, no DVA tester, just an old fluke multi-meter;
Testing the Stator;
Rd/wht to Rd : 67.5 ohms
Blu/wht to Blu: 7460 ohms
Rd/wht to Rd; 21.86 volts AC while turning over
Blu/wht to Blu; 253 volts AC while turning over

Trigger wiring;
White to Purple; 846 ohms (while disconnected from switchbox)
Why w/blck to Brown 850 ohms (also disconnected from switchbox)
All connections to ground were "OL" or 0 ohms.

Blue wire on right side to white on left side; 300 volts
Blue on right to ground 136 volts
Red to Blue 112 volts
Red to Ground 25 volts

Since I don't have a "DVA" tester, not sure I can trust my results for the rest of the test...It may be my next purchase.

Thanks for all the help livetofish Outboard Repair!

[wyoprospector]

Great in depth demonstration. Thank you.

[gilfredooquendo]

Great video I didn't know what it was and to avoid having emotional Damage I just bought everything brand new

[crafter]

Nice work .Process of elimination .Very professional. Brilliant.

[MrJmattr]

Installed Amazon 54$ switch box and it runs perfect now.

[richardwolske]

Great job on the troubleshooting breakdown, 👍

[xBMW]

Very good information everything you needed nothing you didn't

[mikezilla]

Personally if the engine has known to have X amount of hrs 9x’s out of 10 it’s going to be the power box. And ya might as well get new coils and plugs. It’s not a lot of money and what the hell .. if your fixin one thing might as well do a overhaul. Last thing anyone wants is to be out on the water and have to get a tow. Thanks for the run down, it’s always good to know the sequence of operations none the less