Ignition issue, EFI Digital timing

Onexl85

Petty Officer 1st Class
Joined
Jun 17, 2014
Messages
203
Hello all!
tis the season for a boat that won’t start!
Merc 5.0 V8 5.0. EFI Digital timing 2001
serial number M083567

had an issue with it not starting, then it started fine a few times over the coarse of a few weekends. Then yesterday it wouldn’t start once again, did a bit of research this time.

put an in line spark test light between the coil and the Distributer. The light did not illuminate.

checked the poles on the coil, the red lead readers about 14vdc to ground. The white lead shows 13vdc to ground.

the model number on the coil is rubbed off in the end but I’m seeing 392-805570 and the rest is smudged.


is it normal to have positive VDC on both of those terminals while the ignition is in the run position?
 

wingless

Petty Officer 2nd Class
Joined
Jul 7, 2009
Messages
195
This site shows the ignition parts for your engine. The old coil part number is 805570A2. The current part number is 300-8M0079202.

The coil low-voltage terminals will both have the same voltage, 0 VDC or 12 VDC, except when the spark is required, when the engine is cranking or running. That short duration voltage difference causes current flow in the low-voltage side of the coil, which causes the high-voltage to build and the spark to occur.

Does the engine have stored fault codes?
 

Onexl85

Petty Officer 1st Class
Joined
Jun 17, 2014
Messages
203
I haven’t checked them yet.........boat is on the water and didn’t have anything to short the terminals and check the flashes

also......I pulled the high voltage lead off the coil and the pin fell apart. Looked like a bit of corrosion in there so this might be a good start
 

Onexl85

Petty Officer 1st Class
Joined
Jun 17, 2014
Messages
203
Wingless,

when i I put my serial number into that website, I get a different part list for my motor. Different style coil and distributor sensor.
But when I click you’re link it’s exactly what I have! What the heck am I doing wrong?
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
when i run you numbers i get the same info on the ign system as wingless. Standard electronic ign module and standard coil type.
 

wingless

Petty Officer 2nd Class
Joined
Jul 7, 2009
Messages
195
The coil low-voltage terminals will both have the same voltage, 0 VDC or 12 VDC, except when the spark is required, when the engine is cranking or running. That short duration voltage difference causes current flow in the low-voltage side of the coil, which causes the high-voltage to build and the spark to occur.

Does the engine have stored fault codes?
No guarantee on the P/N I provided, but it looked correct to me.

The coil is easy to test w/ a multimeter.

It might be bad, but I prefer to isolate the problem / solution instead of throwing parts at it while hoping.

It is great w/ two engines because swapping parts is very handy to see if the problem follows the part.
 

Onexl85

Petty Officer 1st Class
Joined
Jun 17, 2014
Messages
203
So I picked up a Sierra coil today....all that was available local.

Say on it “use with external resistor” am I useing the right thing?
 

Onexl85

Petty Officer 1st Class
Joined
Jun 17, 2014
Messages
203
Got it, turned out to be the sensor under the distributer cap. Thanks for the help fellas
 
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