How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Tan Your Own Question
Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10618
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
25721800
Type Your Boat Question Here...
Tan is online now
A new question is answered every 9 seconds

I really need some help figuring this out as I am out of ideas

Customer Question

I really need some help figuring this out as I am out of ideas of what could be going wrong. I have a 1995 mercury sport jet 120hp, and It is not getting spark. I have replaced the stator, and the switchbox, and still nothing. Once in a while it will spark but then when you take it on the water it just cuts out and dies, then will not restart.
I found this test on a website:
Keyswitch test
Red Multimeter lead to black/yellow wire from switchbox (wire disconnected from switchbox)
Black Multimeter lead to ground
Turn key in all positions, there should be zero voltage in all positions
There should be zero ohms in off position and infinite ohms in start or run positions
When I did this test, my multimeter showed that their was voltage when I would turn the key to the start position. What does this mean? Is something bad in the stop circuit? I do not have a lanyard kill switch installed right now either. Someone please help me!
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is***** tests are not accurate. The easiest way to test the stop circuit is disconnect the black/yellow from the switch box does spark return?
Customer: replied 1 year ago.
No when I disconnect the black/yellow wire from their is still no spark. The same goes for when I disconnect the black/yellow wire from the rev limiter.
Expert:  Tan replied 1 year ago.
Ok when you disconnect the black/yellow you are eliminating the stop circuit. So that leaves the trigger, stator or the switch box as the cause of the no spark. Since you have replaced the switch box and the stator that leaves only one component the trigger. Just by process of elimination we have eliminated the keys switch, rev limiter, kill switch and the wiring harness. All of this were eliminated when you disconnected the black yellow from the switch box. No need to test the stator it is new or the switch it is new also. Leaving the only and last component of the ignition system the trigger. Does this make sense?
Customer: replied 1 year ago.
What exactly does the trigger do? That does make sense, is their any chance that it could be a bad wire, a bad ground, or something of that sort? I did a ohm test on the trigger and it tested to be still in a good condition. I don't want to just keep buying ignition parts unless I am sure that that part is surely the problem.
Expert:  Tan replied 1 year ago.
The trigger tells the switch box when to fire each cylinder. Now the trigger can pass the ohm test and still be bad. Now since you were able to do an ohm test this tells us the wires are intact. The best way to test the trigger is with a Peak reading volt meter or a DVA adapter for your meter. This is a cranking voltage out put test. Now the DVA adapter runs around $80.00 the trigger is 72.39 on this site. http://www.boats.net/parts/search/Merc2/Jet/120%20%28POWERHEAD%29%201995/0E095088%20THRU%200E141088/IGNITION%20COMPONENTS/parts.html Let me ask another question how are you testing for spark?
Customer: replied 1 year ago.
I have a dva meter, what should it read? Would I test it in AC or DC? I am testing for spark with the spark plug out of the cylinder and putting it next to an engine ground. I know this works because its how I've always tested this motor in the past.
Expert:  Tan replied 1 year ago.
Dc scale the trigger should be 4+ volts. Brown to white/black then purple to white when cranking. The spec for the stator when cranking 180-400 volts depending on the stator for testing is blue to blue white or green/white to white/green. These tests are with wires disconnected and cranking the engine.
Customer: replied 1 year ago.
When I tested each of the two sets of wires I got only .4volts out of them. I tested it on x20. Does this mean that it must be the cause of no spark?
Expert:  Tan replied 1 year ago.
That's the cause of no spark. Replace the trigger. That will get you going. Post back if you need further assistance. Thank you....Tan
Customer: replied 1 year ago.
I just replaced the trigger and still no spark.
Expert:  Tan replied 1 year ago.
Did you buy new parts. These are the only 3 components that have anything to do with spark. Disconnect the black/yellow from the switch box and check the spark. You could have more than one problem.
Customer: replied 1 year ago.
All new parts and black/yellow wires are disconnected. I have no idea where to go from here.
Expert:  Tan replied 1 year ago.
Ok we need to get a DVA adapter to check out put from the stator and the trigger. http://www.boatersland.com/cdi511-9773nl1.html?gclid=Cj0KEQjw2v2sBRCazKGu3tSFz64BEiQAKIE1hpK2Jt18o45ZQeGR3ztsV0x8d4qubF1zR6kYkRDS7Z0aAv6F8P8HAQ
Customer: replied 1 year ago.
I do have a dva adapter. I can re check the stator and check the new trigger for output
Expert:  Tan replied 1 year ago.
Dc scale the trigger should be 4+ volts. Brown to white/black then purple to white when cranking. When you tested the trigger you said the readings came up .4 volts. The spec for the stator when cranking 180-400 volts depending on the stator for testing is blue to blue white or green/white to white/green. These tests are with wires disconnected and cranking the engine.
Customer: replied 1 year ago.
Ok I will do that now and Another thing to add is that the previous owner had a black ground wire running from the ignition switch to the switchbox black/yellow wire. I do not know why, but maybe something is messed up with that. I replaced the main engine harness aswell.
Expert:  Tan replied 1 year ago.
The black/yellow is energized when engine is running if it is grounded on the switch box you will have no spark. On the switch box when you disconnected the black/yellow was the any other wires on that terminal? There should only be the black/yellow on the one terminal.
Customer: replied 1 year ago.
No other wires are connected but the owner before me had the black/yellow disconnected and instead had a new wire he installed from the ignition switch to the switchbox black/yellow, not sure why.
Customer: replied 1 year ago.
The trigger is still putting out only .4 volts like last time, it is brand new though. All 6 magnets under the flywheel are looking normal.
Expert:  Tan replied 1 year ago.
No telling that is usually a sign of a short in the black/yellow not grounding the ignition and not turning the engine off. But we eliminated all of the stop circuits when you disconnected the blk/yel from the switch box. That leaves this as an ignition issue on the engine. The only components in the stop circuit are the kill switch, key switch, wiring harness and the rev limiter. Disconnecting the blk/yel eliminates all of those. The only thing left that hasn't been replaced is the flywheel.
Customer: replied 1 year ago.
I really don't think it is the flywheel, could it be a bad wire somewhere? This is very frustrating and I am just throwing money into new parts that don't need to be replaced.
Expert:  Tan replied 1 year ago.
The trigger isn't producing enough voltage to fire the switch box. The spec is 4+ volts. It is a new trigger then only thing that makes the trigger fire is the rotation of the flywheel. Let me ask you this what have you not replaced? As for the other components you replaced I have no ide how you arrived at then being the problem. I can only direct you to the components you tested. If you tested the stator and arrived at the stator due to it not being in spec then it was bad. The switch box is the last thing you replace if the stator and trigger pass tests. So I found that the trigger was out of spec. This is more than likely from the beginning. So you moist likely didn't need to replace the switch box or the stator. I didn't tell you top replace the other components only the trigger as it was out of spec.
Customer: replied 1 year ago.
I took the flywheel back of and the magnets are very strong. I called a placed and they said in the last 40 years only a few flywheel magnets have went bad. I am just skeptical to buy a new one since everything seems fine with it. The boat ran a month ago but then what would happen is you would start it and then it would just die and you could not start it back up. Is their a chance that the coils are bad?
Expert:  Tan replied 1 year ago.
It's possible but I have never seen that many coils go bad at the same time. My concern is the trigger is only putting out 4 tenths of a volt. When it should be 4 volts.
Expert:  Tan replied 1 year ago.
Do a voltage test to the coils using the DVA meter. If you have no voltage to the coils the coiuls aren't the problem. Have you tested the output of the stator?
Customer: replied 1 year ago.
Is their a chance that the flywheel isn't being turned fast enough? And the stator tests good.
Expert:  Tan replied 1 year ago.
If the flywheel wasn't turning fast enough it wouldn't produce enough voltage. The stator tests good it is turning fast enough. The stator passes the tests. The trigger doesn't so it is the trigger or the flywheel. The magnets for the trigger are in the center of the flywheel not the outside. They are for the stator.
Customer: replied 1 year ago.
Ok that makes sense. The magnets on the inside are not strong at all that must be the problem. Do you know if they should have a pull as strong as the outside magnets?
Expert:  Tan replied 1 year ago.
They won't be as strong as they aren't as big. Everything points to the flywheel.
Customer: replied 1 year ago.
Just installed a new flywheel and didn't change a thing. I have decided to take it into a repair shop.
Expert:  Tan replied 1 year ago.
I don't know you have replaced everything. The only thing it could be is a bad new component.

Related Boat Questions