Strobotest on a Merc 50hp

[ixs]

Taken the engine uot of the water, into the workshop.
Put a stroboscope to the plugs. And had the engine running.
1:st cyl yellow, at tickover, and fading at revs.
2:nd same as nr 1.
Nr 3 and four, almost whiteblue in the light and getting stronger at higher revs.
Changed the red and blue from the stator with blue/white and red/white.
And the problem stayed at nr 1 and 2,.
So, do I change the box?

 

[CharlieB]

Re: Strobotest on a Merc 50hp

Most probably yes, the capacitors for 1 & 2 are dying.

However, since there is NO RETURN on electrical parts you may want to verify this by making a couple more tests.

Switch the trigger leads, if the problem follows the trigger I would not condemn the box.

Switch a couple of coils to be sure it does not follow the coils.

If the triggers and coils pass, then it is safe to order an ignition module.

 

[Faztbullet]

Re: Strobotest on a Merc 50hp

Check the grounds on the coils and swap coils,if still have problems replace the box. Likely bad diode or scr in box. Here is circuit diagram to test diodes and box only has 1 capacitor..

 

[ixs]

Re: Strobotest on a Merc 50hp

Did some earlier tests with my DVA-meter.
Did also swapping coils, and the fault did not follow the coils.

Measurement between cable from box to the coil and earth.
Idling/High speed
Green/Black 254/260
Green/Red 253/260
Green/White 190/106
Green 190/103

Measurement of red and red/white from the stator
Plus on red/white
Idling/High speed
135/230
Minus on red/white
90/230

Measuring between blue and blue/white from the stator
Plus on blue/white
Idling/High speed
260/300
Minus on blue/white
300/270

DVA-measurement on the trigger wires was approx 8V
I did not know which one to put the red prod or the black minus. So I did both ways, and it came out different values.

Hope this shows something, that could help.

Hoping for a nice next boatsummer with all the horsepowers.