Merc Sportjet 120 No spark

[tonym302]

I know this has been answered like 150 times.... and i printed out all responses and tried all solutions offered. <br /><br />The motor is in a BajaBlast and is a Merc Sportjet 120. It has the red stator already (red stator bulletin). I tried disconnected the rev limiter and that did not help. i still have no spark. Took it to a mech and he said CDI/volt regulator was burnt. So i replaced it and no luck. No spark. What are the chances of the big ignition box being no good? it has wires on each side and 4 wires that go to each coil... can i test this box with a meter for resistance?? Any answers will help.

 

[clanton]

Re: Merc Sportjet 120 No spark

You have model/serial number, or photo of ignition system? I cannot id ignition system, the manuals I have show different systems.

 

[tonym302]

Re: Merc Sportjet 120 No spark

ok, off of Cert of Origin<br /><br />1995 Baja Blast<br />Motor: Jet 120<br />Motor No: E099648<br />MFG Serial No: AGCJ1503G495<br /><br />I can get a pic if need be.... let me know and thanks in advance

 

[clanton]

Re: Merc Sportjet 120 No spark

I cannot match this to anything I have, what I need is a wiring diagram of the system that shows stator, trigger, regulator, rpm limiter, switchbox, and coils. This may only be on a service bulletin.

 

[jetdriven]

Re: Merc Sportjet 120 No spark

The ignition box (switch box) can be checked do a degree with meters, but it may be easier for you to test the other components with a meter first. I take it that the mechanic checked out your stator to make sure it is OK. Even the red stators can go bad. A bad stator may damage your regulator/rectifier also. <br />If you have a lanyard kill switch, have you checked it? These can go bad and shut down the ignition. The yellow with red striped wires at your ignition go to this switch. If you unhook one, you will bypass the kill switch.<br />I hope this helps you out.<br />Carl

 

[alounsbury]

Re: Merc Sportjet 120 No spark

I don't know about the red stator - but the standard stator has a low speed (LS) and high speed winding that connect to the switchbox. Basically there should be a blue wire (LS) and red wire (HS) that connect to switchbox - or the switchbox has screws labeled as such. The first test is with a DVA to ensure there is power available to the switchbox - step 1. If you need a DVA check put my previous post at http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=17;t=017922. <br /><br />No power here = no start.<br /><br />The stator also has separate charging windings, unrelated to starting the motor. Basically they just supply charging power to the battery and auxillary stuff (fish finder, etc.) Even if the the regulator is fried - it should still start the motor since independant circuits and windings.<br /><br />If the stator is producing power to the switchbox - next thing to test is the switchbox output to each coil. This should test >180 V peak with the DVA. No output here, means that plug will not fire. If you have power in but nothing out - 2 possibilities.<br /><br />Either the trigger winding (a different coil) is cooked and not producing a trigger signal to fire the plug or the switchbox is defective.<br /><br />To test the trigger windings, use an ohm meter and test the resistance from each trigger winding attached to the switchbox (typically right above the coresponding wire going to the coil on the switchbox) to ground. On mine 90HP - this resistance should be between 1100 and 1400 ohms on each trigger (one per cylinder.<br /><br />Hope that gives you a starting point and good luck.

 

[jetdriven]

Re: Merc Sportjet 120 No spark

I agree with Al's advice. On your red stator, you won't have the blue and red wires. You will have two yellow wires and two others: green/white and white/green wires. The red stator does not have low and high speed windings. The resistance between the white/green and green/white wires should be 600-700 ohms.

 

[kenimpzoom]

Re: Merc Sportjet 120 No spark

There are no tests on the switch box itself. You test eveything else out and if everything else is OK, it is the box.<br /><br />Yes these boxes are crap, I am on my second and it just blew.<br /><br />Get a new one from CDI/Rapair. They are sold at http://www.seilermarine.com/ <br /><br />Also, they make a manual for this engine. Get it, it is pretty good.<br />Ken

 

[jetdriven]

Re: Merc Sportjet 120 No spark

I gave some bad advice. The yellow/red wires do not go to the lanyard kill switch. These wires go to the neutral safety switch in the throttle. The lanyard kill switch wires are black with stripes. Unplug one of these to check the switch. I apologize.

 

[tonym302]

Re: Merc Sportjet 120 No spark

thats ok jet..... I tried that black w/yellow wire and no luck!!!

 

[tonym302]

Re: Merc Sportjet 120 No spark

Hello ken, I was lookin at that site you posted and it listed all the parts.... I know what the stator and rectifier are, but what is a switch box?

 

[kenimpzoom]

Re: Merc Sportjet 120 No spark

The switch box is the "brain" of the ignition system. It takes input from trigger, and sends the high voltage generated by the stator to each coil, which then sends higher voltages to the spark plugs.<br /><br />Very complicated electronics in the switch box.<br /><br />Ken

 

[tonym302]

Re: Merc Sportjet 120 No spark

ken,<br /><br />what exactly is the trigger??<br /><br />I just replaced the switch box and still have no spark.... <br /><br />Any other tips?

 

[jetdriven]

Re: Merc Sportjet 120 No spark

The trigger is another set of coils that are in a small ring around the crankshaft, under the flywheel. The trigger rests in the hole of the stator. The trigger controls when your switchbox should fire for each cylinder. <br />Tony, I don't find where you have reported the ac voltage coming out of your stator. If you haven't checked this yet, you really need to. You have four leads coming from the red stator. Two go to the regulator/rectifier, and two go to the switchbox. To test the stator, unplug the two going to the switchbox, i believe they are green/white and white/green, and hook up a voltmeter across them. All you do is read the AC voltage while you're cranking the engine with the starter. If it is 150-180V you're fine. There is also a red stator adapter that these stator wires plug into to lower the voltage for the switchbox. You can check the voltage coming out of that adapter on the blue wire, too. I don't remember what the voltage should be, but it is probably around 79-90 volts ac. <br />Alounsbury gave good advice about testing the trigger.<br />If you don't have a volt/ohm multimeter, you can get one at Wal Mart or Radio Shack for $10-20 that will do the trick. You really need one of these if you don't have it.

 

[tonym302]

Re: Merc Sportjet 120 No spark

thanks jet.... I have a multimeter tester.... the question is, what do i set it on?? I think someone mentioned Ohmsx1000 in a previous post. this true?

 

[tonym302]

Re: Merc Sportjet 120 No spark

ok, ran a quick test on it.... i used the yellow/green and the green/yellow wires. set the meter on ACV 750 and the readout was 16 while cranking the motor. I hooked up these wires back up. Then i tested the wires coming out of the reducer/adapter. These tested the same 16 at ACV 750.<br /><br />To be sure, I have to hook up the one wire on the positive side of the meter, and the other on the neg side of the meter. Right? If so, why was the voltage the same.

 

[jetdriven]

Re: Merc Sportjet 120 No spark

I'm not sure why the voltage was the same. It may be that the red stator adapter is some type of step-down transformer that only lowers high voltages. I have never found a description of exactly what that adapter does to reduce the red stator voltage to that of the original style stator. I think that you have probably proved that your adapter is OK though, since it flowed current. If you had no current flowing through it, it would have been preventing any voltage from getting from your stator to your switchbox.<br />If your meter set on AC750 reads exactly the voltage put out, than your stator is bad. You may want to test the meter in a wall socket if you're not sure. It should read 115-125 volts AC in the wall. It just seems odd that you are getting 16 volts when the correct number is approximately 160 volts (16 times 10). If you're sure that you only have 16 volts of output, then your stator is bad and needs to be replaced.<br />About your ohmsX1000 question, that is fine for testing the trigger resistance if that is what you're wanting to do. You can also test the stator resistance, which should be 600-800 ohms across your greeen/yellow and yellow/green leads. This may help you to further diagnose your stator condition.

 

[tonym302]

Re: Merc Sportjet 120 No spark

ok jet..... i just stuck the meter into a wall outlet and it spiked to 117 volts on the ACV 750. I will retest it tomorrow when i have more light, but at this point, my stator might be at fault. Does this sound right to you?? Thanks for all of your help.

 

[rickdb1boat]

Re: Merc Sportjet 120 No spark

Need to set Meter on Lower AC setting. I don't think you could hardly read 16 Volts, when set on 750. Try the lowest one that will allow 160 Volts to be read(240-250), something like that, depending on the Meter. Or spring for a digital meter. Much more accurate!

 

[tonym302]

Re: Merc Sportjet 120 No spark

it is a digital meter will a readout 'hold' button.