Need advice, 1996 125hp no spark now, won't start

[1207]

I have a ~1996 125 hp Mercury outboard turns over but doesn't start. It has gas and the hose bulb feels full after a few squeezes. The run/stop toggle is on "run", there is no lanyard type kill switch. I took a plug out, cranked the motor and saw no spark when grounded to a bolt on the block. Its sunny so a spark might be hard or impossible to see. When I first tried to start it, it seemed to fire once right at the beginning but after that nothing. Afterwards I noticed that the negative cable on the battery was very loose so I wonder if an instantaneous, arcing, contact or loss of contact might have blown a fuse. However, the owners manual only mentions a fuse for the start circuit where the starter will not turn over if it is blown. That is not my case, the starter spins the engine normally. I wonder if there is another secret fuse the owners manual doesn't mention that controls power to the coil or some electrical component that makes the spark. It sure acts as though there is no spark. The engine has been a reliable runner for 20+ years. It ran fine the last time I was out in June, now it was just that one momentary, initial, fire then nothing. Is there another fuse for the ignition or is my coil or something else haywire? Thanks. Eric

 

[Chris1956]

On your motor, a single stator with multiple windings powers both the ignition and the battery charging circuit. A loose negative battery cable can easily damage the voltage regulator, causing a possible short impacting the ignition.

I would disconnect the VR from the stator and insulate the yellow stator wires. Now see if spark has returned. If not, there is a CDI Electronics test for stator and switchboxes.

 

[1207]

Chris, thanks for the reply. I'll let you know the results of your test when I get to it. The boat is on the water so waiting for a quiet day is much easier to work on it while hanging over the transom.

 

[1207]

On your motor, a single stator with multiple windings powers both the ignition and the battery charging circuit. A loose negative battery cable can easily damage the voltage regulator, causing a possible short impacting the ignition.

I would disconnect the VR from the stator and insulate the yellow stator wires. Now see if spark has returned. If not, there is a CDI Electronics test for stator and switchboxes.

Chris, thanks for the reply. After all the summer activity I got around to doing the test you mentioned. It wasn't clear to me which leads to disconnect so I disconnected all the leads from the voltage regulator, took out a plug and grounded it to a shiny metal bolt on the block. Cranked the engine and got no spark. Then I connected all the leads back up to the VR except for the two light green leads which I assume are the "yellow from the stator" you mentioned. (there are no yellow leads on my VR). Still no spark.

You suggested a CDI Electronics test for stator and switch boxes. It looks like CDI is a manufacture of testing equipment. Do I have to buy a test device to do any further diagnosis? I have an Equus 3310 digital multimeter if that is sufficient. How would I proceed without any special DCI equipment?

Thank you

 

[Chris1956]

CDI Electronics is a manufacturer of stators, switchboxes and other stuff. Their test procedures are designed to help you figure out which of their components you need to buy to fix your motor.

As far as I know you only need a DVA to test your ign system. There are instructions on this forum on how to make one.

 

[richw46]

My 1995 115 Mercury started having starting problems last fall. This spring the motor quit running so I ran some tests.

On the right/starboard side of the motor there should be an enclosed, inline, fuse holder. check that. You say there is no lanyard for the run/stop kill switch? You need to fix that. New boating regulations require it to be there and connected to the driver when underway.

There is a test for the stop circuit. The switch box (power pack) is on the starboard/right side. As you face it, about halfway down, left column, there is/are 1 or 2 black wires with yellow tracer line. These are for the stop circuit. One goes to the ignition switch, the other to the rev limiter, if your motor has one. Disconnect both wires from the switch box. Connect your multimeter positive lead to each wire (1 at a time) and negative lead to engine ground. Turn the ignition key to 'on' but don't start or crank the motor. The reading should not be more than 2 VDC. If so, you have a problem in the stop circuit.

I have a black stator. I think later models have a red one. For my 1995 with a black stator I did a continuity test between the red & red w/white tracer and the blue & blue w/white tracer. There are 2 wire bundles coming down from under the flywheel; stator and trigger. On my motor the stator bundle is at the rear of the flywheel, trigger is on the right side. The stator's red wires showed continuity, the blue ones (which are low speed) showed no continuity. (I'm attaching pics from the shop manual. I didn't get the readings they show.) The new CDI stator did show continuity and replacing the stator with the switch box solved my problem. (Mercury recommends replacing both at the same time because if one is bad it can damage the other one.)

I just released a video on replacing my stator and switch box. It may help if you need to go down that road.