Mercury 1979 402 40hp spark problems

[bcbart82]

Hello,

Im looking for some help diagnosing a spark problem on this engine. Im not getting spark. I replaced the stator last year simply because the wiring was completely rotten. After that i didnt use the boat much but it ran. Then one day it just died. I checked the orange kill wire as recommended to see if it was an ignition problem and still nothing. I then removed the two yellow wires from the rectifier and instantly i had spark. I replaced the rectifier and with it hooked up still no spark? Any assistance would be appreciated. (2 years ago i replaced the engine wiring harness due to rotten wires)

Bart

 

[bcbart82]

According to the CDI electronics it should have fixed it after replacing the rectifier but it did not. If i unhook the rectifier it starts and runs. Weird.

 

[bcbart82]

Any help on this? The boat will start right up with the rectifier unhooked. With the dva i dont get good voltage with the rectifier hooked up. Unhooked i get higher but not in spec then unhook the switchbox and i get voltage in spec. Can the switchbox cause this? (I think its a 1978)

 

[jimmbo]

The Switchbox and the Rectifier are wired to separate Coils on the stator. Yellow for the Rectifier, Red and Blue for the Switchbox. I'm more inclined to think the Stator or wires to the Stator are the issue

 

[bcbart82]

Thank you for your help. Even if the stator is brand new? I guess its possible.

 

[Ksanthony]

Having just went through this I can attest to the same thing. I removed my rectifier she ran like a top I bought a new one and she ran like crap. I disconnected the new one and off she went. I have a separate thread going on here but the gentleman there is saying the ground on the rectifier has to be tight and complete or they will blow instantaneous. That is what happened to mine. Deep in the CDI trouble shooting pages I stumbled upon a note saying the rectifier will cause these kinds of problems. Their solution remove rectifier if problem goes away replace rectifier.

 

[bcbart82]

Ksanthony i read the same thing in the CDI troubleshooting guide. I just put the new stator on last year and the boat ran for 10 minutes and died. As far as i can tell with my meter there is nothing wrong with my new stator unless im missing something. Mine will start right up as long as you unhook the rectifier. Thanks for your response.

 

[jimmbo]

In your earlier posts you stated you have replaced both the Stator and the Rectifier. In a later post you say the Stator checks out with the meter. How does the Rectifier check out? A Rectifier can test fine with a multimeter( low voltage), but fail when hit with the higher voltage and current from the stator, and using a test light(head light) that can draw a higher current could reveal a bad Diode.

 

[Ksanthony]

BcBart82, I checked my grounds for the rectifier and discovered I had an intermittent open when trimming the motor. Upon farther look I found one of the ground cables connecting the bottom cowl was off, now that that is fixed I am waiting for a new rectifier to see if that solves my problem.

 

[bcbart82]

I have a dva and multimeter i can try that im just not sure if i would set the meter for dc or ac since thats what the yellow wires from the stator provide also keep in mind it will not start with the yellow wires hooked to the rectifier so im only getting cranking readings. Thank you both for your help and responses.

Bart

 

[jimmbo]

AC is what is coming out of the Stator going into the Rectifier, DC is what is supposed to come out of the Rectifier, but it will still be of varying Voltage

 

[bcbart82]

it has to be the stator. I bought a second rectifier and that didn't help . I get continuity on the two yellows (beeeep) and voltge that tells me it's consistent when cranking. I put both yellow wires to ground on the engine and it was the same as hooking them to the rectifier no spark. Hooked together but not grounded and spark. What else could it be other than the stator being shorted by the yellow wires? Shame that stator lasted ten minutes?

 

[jimmbo]

Putting the two yellow wires together like you did put them together is a dead short. So is putting both of them to the block. The Rectifiers used on these engines appear to be rather Fragile and will burnout instantly if the battery is hooked up backwards.

You replaced the Entire wiring Harness a couple of years back, then a year later you replaced the stator, in both cases because of bad wires? Did you run it after you replaced the Wiring Harness?

 

[jimmbo]

Is it an Electric Start or a Rope Start?

 

[bcbart82]

The motor is an electric start. I've had the boat on the water and running after changing the engine wiring harness. This problem resulted after changing the stator and just running on the muffs in my driveway. If I get a chance this weekend I will try to write down the values I get with my meter. I'm quite sure I get a little over spec with the diva on the blue wire cranking with it unhooked from the box but spec reading on the red. If I hook the box to the stator both numbers are lower then with rectifier hooked up very low cranking volts. Reading ohms on the stator set at 200 I get a good reading on the red wire but when hooked to the blue wire and ground I set the meter to 20,000 or 200,00oto get a reading and it's not 5-6000 it's like 50? I'll have to double check that reading Thanks for your help.

 

[bcbart82]

I do have a service manual and it says ohms on the blue wire should be 5-6 with a meter set at Rx1000 of course my meter doesn't have that setting. That value is also for OEM not sure about a sierra brand stator?

 

[bcbart82]

I have a service manual that says ohms on the blue wire should be 5-6 with the meter set at Rx1000 of course my meter doesn't have that setting. That would be for OEM the stator I purchased is a Sierra brand.

 

[bcbart82]

[No message]

 

[bcbart82]

Those reading are the stator like a bench test

 

[bcbart82]

Does anyone know why the CDI and most other troubleshooting diagnostic charts for this engine show the stator check on the red wire to ground as being 180-340 and my Mercury manual shows 50-60? Could it be the type of meter used when the older manual was written?