how can i check this box to see if it is bad ? its a 1983 merc. 70hp. the boat was running fine , then i shut it off and it wouldnt start again. i have no fire from any of the 3 coils. thanx mike
Do you have any corroded or broken wires going from the pack itsself or the coils? Check to make sure all wires, including grounds are tight.....Bare wires with insulation falling off or melting can kill a pack quicker than anything
I don't have that particular motor, but if all three coils aren't firing, I might start looking at the rotor and not the power pack. The power pack does provide fire to all the coils, but they are largely three separate circuits. Your rotor going bad would stop sending signals to the coil and it wouldn't fire any of them.
You might check out this post, although it is for a different HP motor, the concept will still apply.
you can test the kill switch. Stick a meter across the wires. If it's bad, (meaning constantly pressed) you should read zero ohms. If it's good, you should read an open. Worst case scenario, you could clip one of the wires and test it. Then just resolder.
The ideal setup would be to have a o'scope. Now I realize that not everyone has access to this particular piece of troubleshooting equipment. Barring having that, if you place a meter on the leads and look at AC, you should see a change when you crank the engine as the rotor passes the stator. It won't be definitive, but it will tell you whether or not you are getting a pickup.
ok , i can do that. i should set the multimeter to read 12 volts dc, correct? what range of numbers should i see? question for you ! doesnt a wire from the stater go directly to the switch box? i believe either blue or red . i should be able to check it at the switch box ??? thanx, mike
Your original question was how to test the box, start with buying a DVA then disconnect the black/yellow lead from the box next test the inputs from the stator inputs red =25v + v./ blue= 180 + v. / each trigger wire +4+ v. and each output should be 150 volt. Not so hard after all.
Are you using a DVA as the stator voltage sounds low which is not a suprise but the trigger voltage being low I think might be a faults reading as they never have problems in all 3 seperate windings at the same time.
I've got a DVA question for you? What is in the DVA that allows it to see peak voltage? If you have a true RMS voltmeter (newer one) couldn't you just multiply it by the inverse of .707 and get peak? I've never used a DVA, so I'm unsure as to why you must have one.
The one item it didn't test until today is the rectifier. Turns out I do get a bad reading on one of the posts. Could a faulty rectifier prevent the engine from firing?
Mike, A shorted rectifier can keep a engine from firing but if you disconnect the yellow wires then the spark should return, if the short has not damaged the stator.
Mark, I don't know about the factor for sure but some of todays newest meters are equipt to read peak voltage and can read the system without a DVA.
Good stuff! I'm heading home in a couple hours to trouble shoot my 50hp merc that has no spark and I'm gonna add this to my arsonal that I have established by using the search engine on this site the last couple day's. Laddies, your willingness to share your knowledge and help others is much appreciated.
