95 30hp 2 cyl Mercury - No Spark

[59 lonestar]

First, I'm a total amateur. I have the service manual, and found a great post on troubleshooting that some had under the common problems forum. But for the most part I'm shooting in the dark.

After de-winterizing I had a little trouble with what I thought was an old gas problem. I wasn't getting enough power in the cylinder, and I had a little revving at lower speeds. Then I replaced the gas and really smooth cruising for about 2 hours. Then without any other symptoms, she just died, almost like the kill switch had been hit. No chugs, nothing.

I'm not getting a spark in either plug.

Last year I replaced one of the two CDMs, and the symptoms included choppy running, but at least starting. I've got no spark now.

Switched the plugs. I flipped the kill switch a bunch. I disconnected & reconnected all of the harness connections at the engine, checked, and there don't seem to be any loose ground cables. I opened the control box and disconnected the kill switch (black / yellow cable), didn't reconnect, tried to turn it over. (should I have done something different here?).

Tested the ohms on the stator and it was supposed to be between ~500 - 600, I had a reading closer to 1,500.

1) Does a stator just crap out like that?
2) It feels like the kill switch, or something simple just given the way it died, but maybe I'm not testing it right? Any advice on how to actually test it is appreciated.
3) Other ideas or ways to test for a more simple fix than stator, or does the ohms test just sum it up?

Thanks.

 

[Iceman66]

Re: 95 30hp 2 cyl Mercury - No Spark

Possible bad switch-box,but look at this:



CDI Electronics Practical Outboard Ignition Troubleshooting

 

[JDusza]

Re: 95 30hp 2 cyl Mercury - No Spark

+1 on cdielectronics.com

Don't spend any money until you've got the troubleshooting done. Throwing in a statos means $200. be sure before you spend. It's worth the meter and DVA to get this right.

You can do it!
J

 

[59 lonestar]

Re: 95 30hp 2 cyl Mercury - No Spark

Thanks for the reference.

 

[1nebel0]

Re: 95 30hp 2 cyl Mercury - No Spark

Take the yellow and blk wire off the switch box to check the kill circuit...to lose both cylinders will be a stator but check it as stated above...

 

[59 lonestar]

Re: 95 30hp 2 cyl Mercury - No Spark

I'm off to visit the motor. I will recheck the kill switch and confirm the resistance and DVA.
As a side, do stators just die without symptoms?

 

[Anchor Marine Repair LLC]

Re: 95 30hp 2 cyl Mercury - No Spark

Yes a stator from Mercury will just die like that. I can't say I'd jump to a bad stator with that reading. Too many human variables in that tight perameter. Was that disconnected wires or connected?

It looks like from your statement "I replaced 1 of the 2 CDMs " that you don't have a switch box motor. You have a CDM for each cylinder. They are small like a coil, 1 per cylinder. Serial numbers are crutial on Mercury's hint hint

I'm trying to help, under that assumption.

If you read through the theory of operation page Boatinfo - Mercury Service Manual for 30-40hp 2 cylinder you'll note that one bad CDM on a certain circuit will give you no spark to both the CDMS. So be sure to resistance check both of those CDMs per the Mercury manual.

Always replace CDMs as a pair, or the one will take out the other, since their SCRs would have minor resistance differences. This is on even number cylinder motors. A 3 cylinder doesn't do this. The return path of voltage to the stator is through the other CDM. In other words, the one provides ground to the other. If you take a simple 12 volt light bulb with 2 wires accross a battery, it will light up. Remove the ground- no light.

You might be fighting on 2 fronts here, the mismatched CDMs and a number of other variables.

If this has an external Rev Limiter box, then take that out of the equation.

Test your trigger for resistance as well, since they share a ground. A bad ground on your trigger will give no spark to either CDM.

 

[59 lonestar]

Re: 95 30hp 2 cyl Mercury - No Spark

Anchor - your advice pulled me back from the stator, and back to the CDM. Thanks.

Two things initially sent me to stator - 1) My service manual says that if there is no spark in either cyl, that I should look upstream (so the link you posted was a better trouble shooter), and 2) last year I replaced one CDM, but motor still ran - albeit very rough. So, I concluded that with one CDM, you still get some action.

My process: In addition to the meter readings (could not do DVA), I finally disconnected both CDMs and one at a time put them first in series plugging directly into engine wire connection (instead of the daisy chain where the second goes into the harness of the first) with the spark plug connected to the coil and the coil in hand I checked for spark (the old fashioned way - by feeling it). The CDM I replaced last year gave a jolt whereas the old one had nothing.

So what was different from my experience last year when one CDM dies, but the motor still ran for a while, very rough before cutting out and this time when I got absolutely no spark anywhere?
Here are the facts: The CDM replaced last year was on top and second in the series. Only by removing the dead one this time and putting the good one first in series was I able to get a spark. One of two theories - either the dead one "being first" impacted the second's ability to get a spark, or the dead one had a faulty kill and that killed them both. I think the latter is the case, but interested in other opinions.

Now, it's not final, but it does point to at least one bad CDM. There could be more going on, but only after I replace will I know this weekend.

Thanks all.