Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

[LCCRUISER]

Hi,

I bought a 1985 SeaNymph SS-175 just over a week ago powered by a 1985 or 1986 Merc 90 HP inline 6 based on the serial number. It ran fine on the test run, although it was a bit hard to start from cold. I had read that motors have individual personalities related to starting, so I wasn't really turned off by that. (My mistake!) Once warmed, it started fine with a blip of the key.

I used it a few days later and ditto, although it started even harder. It ran fine and started mostly OK after warming. Since yesterday, it won't start at all.

I have spark on only cylinder 2 (from the top) and no others. This "Tower of Power" is a CDI engine with 6 individual coils, 2 switch boxes and NO distributor.

I have a Seloc manual for reference. Compression is 135-140 on all cylinders. It is a dual battery setup and cranks quickly and for a long time.

I cleaned all terminals on the switch boxes and coils even though most looked fine. Resistance values per Seloc and CDI Electronics seem to be within spec.

I jumped the wire that goes to the coil 2 terminal from the upper switchbox to all the other coils and I get strong spark from all other coils. I believe that confirms that all the other coils are are also good. However, I can't get a spark from any other switch box terminals regardless of which coil I jump to. I have also ruled out bad plugs by testing them.

The question is, are both my switch boxes trash or should I consider stator, flywheel, rectifier or trigger prior to replacing them? I don't want to replace and hope, I want to diagnose and resolve.

The prior owner had this motor serviced by the local Merc dealer this Spring. I also have prior experience with them that makes me a bit shy on their level of service. I'm not about to run back there soon. My diagnostic equipment is limited to a voltmeter/ohmeter, 12V continuity tester and a spark tester along with a bevy of hand tools and gray hairs from past experiences ;>)

I'm patient, but a fishing trip to Cape Cod in a week has put me under the gun to get this fixed ASAP. I'm also retired, so $ is an object. Any help and suggestions would be greatly appreciated.

Thanks!

LC

 

[arsenalpsu]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

You need to test the stator & trigger, is the procedure in your manual? I don't have the time now to type up how to do it, go to the CDI web site and read their papers on how to test if it's not in your boo,. If your stator tests ok you'll need a DVA tester for the boxes. pretty expensive if you buy one, very cheep to make an adapter though. (4 bucks) If you have a bad stator you can not test the switch boxes, so we can't tell if they're bad until we know you have a good stator & trigger.

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

Thanks for the input on the DVA adapter and CDI. I am going to Radio Shack to see if they have the parts to make one. If not, I will have to buy one online or a multimeter that reads peak voltages.

Are the voltage readings for the DVA taken as DC or AC?

So far I have tested the following:

1. Trigger continuity. All within specs.

2. Stator continuity. All within specs except I have an open circuit between blue/white and red/white leads. It should read about 6K ohms, it is infinite. That could indicate a bad stator.

3. Swapping red/white with red and blue/white with blue per CDI suggestion makes no change. I still have spark on only #2 cylinder.

4. Disconnecting rectifier made no difference.

Thanks again!

LC

 

[Coloradolakeboy]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

.

Are the voltage readings for the DVA taken as DC or AC?
LC

Here is the answer achris posted to my DVA question here

"If you don't already have one go and buy a cheap DMM (Digital multimeter). You need it set on the '600 VOLTS' range (as shown in the drawing with the build instructions)."

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

Thanks! I have 2 multimeters with sufficient capacity. The Shack didn't have the capacitor in the higher voltage needed, so I am back to buying the online adaptor.

 

[arsenalpsu]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

you should be able to find an adapter for 25 bucks. They're only 3 parts to the thing, my radio shack didn't have the parts either, had to go to an electrical supply store but it does work. You need to test in AC, without a DVA when you test the voltage from the boxes the meeter will just jump all around. If your stator failed the first test I bet that's the problem. If it were the switchboxs it's highly unlikely both failed at the same time (but not impossible) When you get your adapter recheck the trigger, ohms is good for a quick check but the output voltage from a DVA is the only sure way to make sure it's 100% good.

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

When I check the voltages with my needle type meter, I get steady readings while cranking. Is that possible without the adapter?

The readings are as follows:

Red & Red/White = 35V. Blue = 200V. Blue/White = 1V

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

I picked up another fire today, not sure why. Number 5 is not only putting out a spark, but it fires a lightening bolt right out of the end of the empty plug boot without even being close to a ground. Not sure why that happened, but #2 and #5 share a trigger coil. I was hoping it might fire if 2 cylinders were working and then produce more spark at a running RPM, but no go.

I also built myself a DVA adapter today. It worked fine once I installed the diode in the right direction. Either the online schematic is wrong, or I am misreading the polarity of the diode symbol. I'm not sure if it is my meter or the dapter circuit, but my multimeter died after I took some readings. It won't even register continuity anymore (yes, I checked the battery). It was fun while it lasted.

Before it died, I obtained the following readings:

Red & Red/White wires (high speed coils) = 25V which is within spec. The (low speed coils) blue wire is only 120V and the blue/white is a paltry 90V. These latter 2 are supposed to be 180V.

The trigger resistance from black sleeve wires to yellow sleeve wires are within specs. The DVA readings are 1.5V, they are supposed to be 4 or more.

All the black sleeve and yellow sleeve to ground read 15K ohm. They are supposed to read very high or open. They are all supposed to read 1V on the DVA and they do.

I'm not sure where all my resistance and voltage readings are leading me. I was convinced I only needed a stator due to the the lack of any continuity between the blue/white and red/white wires. I'm not sure how that issue affects the trigger readingsose affecBut the trigger readings , but it may be a trigger problem as well and/or the switch boxes. Anyone have an thoughts?

Due to the fact I have only Wed and Fri to resolve this before taking the boat on vacation, I am ordering everything. The overnight shipping is killing me, I'm up to $140 just for that! Everything should be here Wednesday morning.

I will order a DVA multimeter tomorrow first thing when the supplier opens. I ordered the flywheel puller today. I have also ordered the trigger, stator and both switch boxes. I will try to get new readings with my new meter before tearing it apart. If that doesn't work, I am going to replace the stator and hope that solves it. If not, I will retest and proceed with whatever part(s) are called for. The parts are returnable if I don't install them, so I hope I don't need anything beyond the stator.

I have been reading about a mercury switch (a/k/a tilt switch) and a kill switch which is also mercury. They are in my Seloc shematics. I can't figure out if the tilt mercury switch at the motor end is for the tilt motor or part of the kill circuit. My manual references a black/yellow wire that goes to a kill switch, but I can't find any black/yellow wires at the engine end except on the enrichener circuit.I have a single lever control with a button on the lever to allow throttling up without shifting into gear. Plus it has a tilt button. There is no deadman's kill plug, although there are 2 loose wires taped of that might be for that. Is there any possibility that a problem in the kill circuit could kill all but 1 or 2 cylinders?

This is my first time delving into any kind of electronic ignition, so any help is appreciated. I'm beginning to think that I would rather have a motor with a distributor, points and condensor or an unlimited budget so I don't have to work on the damn thing myself. On the other hand, if I figure out how to resolve this type of problem, I might be able to get some good buys on "dead" motors that have good compression and won't fire.

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

Problem resolved!

Replacing stator upped the voltage on the weak side, but still no fire. I replaced both the switch boxes and had spark on all 6. She fired up so fast I couldn't believe it was the same motor. It revs fine and and settles into a low idle without any issues, in gear or in neutral.

Unfortunately, during this whole exercise, the solenoid has taken a crap. It clicks, but won't operate the starter. I can jump the starter and she cranks twice as fast as before the solenoid gave up the ghost. Hopefully, one of the local dealers has one.

In the event of a future breakdown, I have the 9.9 kicker as a backup.

I will be returning my unopened trigger after I return from vacation. I will also be buying another boat. I have a line on a 1989 Hobie 18/19 Power Skiff for $3500 and a late 1990's Maritime Skiff for $4500. I tried the Maritime 3 weeks ago and would have bought it, but it was $5500.

 

[asm_]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

I noticed you also built a home made DVA adapter. Do you mind sharing the size of the capacitor and resistor value for your unit? I just built one over the weekend, but have tried 1uf and 3.3uf. The reading seems to jump all over the places.

 

[asm_]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

I'm not sure where all my resistance and voltage readings are leading me. I was convinced I only needed a stator due to the the lack of any continuity between the blue/white and red/white wires. I'm not sure how that issue affects the trigger readingsose affecBut the trigger readings , but it may be a trigger problem as well and/or the switch boxes. Anyone have an thoughts?

Since you have solved your problem, not sure it you still want to know.

In any case, blue/white and red/white should be open. They should not be connected. They are both connected to ground. Think of them as two different stator coil with different winding count to produce voltage/current at different RPM. With all that said, I have found resistance reading to be extremely unreliable for determining the state of ignition component.

B

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

The open circuits were between the blue/white and ground and red/white and ground, not between each other.

As to your other question re the dva adapter I built. I used a 2.2 mfd and 1K resistor. I found the store bought meter with the dva built in far superior and more reliable.

 

[asm_]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

As to your other question re the dva adapter I built. I used a 2.2 mfd and 1K resistor. I found the store bought meter with the dva built in far superior and more reliable.

Thanks for the info. I'm using 3mfd and 5m ohm resistor. I did first use 1m ohm resistor, but the reading was dropping too fast to be read by my meter. Switch over the 5m ohm resistor solved that problem.

Also, I contacted CDI and inquire about how to use their DVA adapter, and they say to take the measurement while cranking, or 300RPM, not in fast idle like I did. Which it makes sense as engine generate a lot more EMI while running. Which it explains the erratic reading I have observed.

Hopefully someone may find this info handy some day.

B

 

[SeaKaye12]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

LCCruiser....

What model DVM did you end up with?

Thanks, Chuck

 

[LCCRUISER]

Re: Mercury 1986 90HP Inline Six (6) Won't Start - Spark only on 1 Cylinder

LCCruiser....

What model DVM did you end up with?

Thanks, Chuck

I bought the ESI 530 from US Tool Warhouse. The price was right and they were easy to deal with. I was originally going to buy their DVA adapter and ordered one just before 5PM. Then my meter quit on me that evening. I called them when they opened the next morning to change the order to the ESI Meter instead. They changed the order instantly without hassle, the meter went out the same day and was at my door the next morning. I'd recommend them to anyone.

The meter itself is light and simple to use. I would imagine the quality may not be up to the OEM's or some other makes, but it was only $80 plus shipping. Some of the range values are lower than a high quality multimeter, but s I saw them mentioned on the forums as being OK, so I figured it was worth a shot, especially on sale. It comes with a single AA battery that you have to move from an empty battery slot into the one that is wired. One lead has a clip on the end and the other has a probe.The manual is very simple and assumes some prior knowledge in the use of a meter, but not necessarily a DVA.

If you aren't a professional marine technician, I would think this would serve your purpose adequately. And I'd like to reiterate my great experience at usatoolwarehouse.com and recommend buying it from them.