RPM at cranking speed

[Merccoper]

Hi All
My 1996 40 hp Mariner Magnum has no spark.
I’ve now got the shop manual and going through the diagnostic tests. I’ve tested each of the components and they all appear to be in spec. By process of elimination, this suggests the Switch Box is the issue (as the switch box itself can not be directly tested)

There is one diagnostic (Stator Low Speed and High Speed Test) that would ‘help’ confirm the Switch Box as the issue. The tests need to be done at 300-1000 rpm and 1000-4000 rpm

 

[jimmbo]

I am curious as to how one would spin an engine faster than cranking speed, without it actually running, which in itself means the Switchbox is functioning.
I will assume the testing of the Switchbox is actually done with specific Electronic Test Equipment

 

[racerone]

Charge the battery and load test the battery.----Easy ( in my opinion ) to take the starter apart for inspection.----If flywheel does not spin fast enough there will be no spark.

 

[jimmbo]

It doesn't have to spin very fast, as even engines larger that that can be rope started.
I used to rope start my 84 115 inline 6, as I was too cheap to replace the Battery, and it was an ADI system

 

[dingbat]

The high speed winding isn't your problem if you have no spark.
Lost the high speed windings on a 175HP Merc 20 miles offshore.

Motor started and ran perfectly fine up to ~1,500-1,600 rpm.
Long, long ride home.

 

[Merccoper]

I am curious as to how one would spin an engine faster than cranking speed, without it actually running, which in itself means the Switchbox is functioning.
I will assume the testing of the Switchbox is actually done with specific Electronic Test Equipment

from what I understand, the only real way to “test” the switch box is by eliminating the other components.
I think the manual should preface the test by saying something like…do this test if engine runs.

 

[Merccoper]

Charge the battery and load test the battery.----Easy ( in my opinion ) to take the starter apart for inspection.----If flywheel does not spin fast enough there will be no spark.

Thanks. Got it on the charger now.

 

[Merccoper]

The high speed winding isn't your problem if you have no spark.
Lost the high speed windings on a 175HP Merc 20 miles offshore.

Motor started and ran perfectly fine up to ~1,500-1,600 rpm.
Long, long ride home.

Must have been a nerve racking trip!!
I’ll test the low speed by cranking and see what I get. I’m getting more confident that it is the switch box

 

[Merccoper]

Hey I have this same problem I have red stator with attachment everything seems good just bought dva all seems good blue adapter wire goes into switch good got nothing coming out on green wires to coils all triggers tested good. I am new to this boating thing but used cdi electronics troubleshooting guide.

I gave the black stator.
As I mentioned, I think if you do all the component tests (and you are confident in your tests) it only leaves the switch box as the issue.

 

[Merccoper]

By the way I have a mercury 75elpto with electric start I see in so.e schematics talk if mercury switch I don't see one. Are where one would be wired into kill circuit I do have atilt position sensor

My engine doesn’t have the mercury tilt switch….I think previous owner removed it

 

[Meggerd]

Did you use the dva adapter on meter it seems to be an absolute in diagnosing these, from all I've read

 

[Merccoper]

Did you use the dva adapter on meter it seems to be an absolute in diagnosing these, from all I've read

Thanks for the input. From what I can understand from the service manual, a DVA is useful in some situations. The DVA is used to help isolate which component you need to test but not used to test a specific component. A more time consuming route is to test each component. AND, I think if you have no spark (rather than a week spark), you can do without the DVA.

I welcome any input if my thinking is incorrect.

 

[Meggerd]

Well I did test each individual component the motor runs off stator it induces voltage to ignition through magnetic induction and uses it to charge battery Through rectifier and run ignition system through switch box to coils and the triggers tell the switch box when to send voltage to coil in right firing order

 

[Meggerd]

But that is just basics as I understand It I am a lamine it's all new to me on this boating thing looking for clarification also

 

[Merccoper]

Well I did test each individual component the motor runs off stator it induces voltage to ignition through magnetic induction and uses it to charge battery Through rectifier and run ignition system through switch box to coils and the triggers tell the switch box when to send voltage to coil in right firing order

You need (I think) to test the ohm’s for each component (stator, trigger, mercury switch, ignition switch) as per the service manual for your specific engine in order to determine if they are functioning correctly…..I think….I’m not an expert.