2005 4.3 liter Mercruiser ignition trouble

[kepruno]

Get a 12-14 gauge jumper wire with alligator clips and clip one end to the same terminal on the key switch, the other end to the positive terminal on the ignition coil. Just run the wire right across the boat. Bet it starts.

I bet you are right but I don’t think that will tell me where the problem is. I now know I’m losing power somewhere between the switch and the coil. That kill switch seems awful suspect? Does anyone have info on how to get it out without wrecking it.

 

[kepruno]

Not my boat but it looks very similar to this. Mine has a pad behind it that I guess is for your arm.

 

[alldodge]

I bet you are right but I don’t think that will tell me where the problem is. I now know I’m losing power somewhere between the switch and the coil. That kill switch seems awful suspect? Does anyone have info on how to get it out without wrecking it.

Correctly I don't see how the kill switch is the problem because you said

Every wire except the purple has or gets 12 volts when the key is turned to start. To further clarify, every single wire is disconnected except the power.

The purple is not getting power so it's currently not the kill switch

 

[kepruno]

Correctly I don't see how the kill switch is the problem because you said

The purple is not getting power so it's currently not the kill switch

That’s when I had my head up my ass and I was checking the wrong purple.
I should have said every connection except A gets power when the key is turned to start.

Currently have power at the switch (I), not at the coil.

 

[nola mike]

That’s when I had my head up my ass and I was checking the wrong purple.
I should have said every connection except A gets power when the key is turned to start.

Currently have power at the switch (I), not at the coil.

I think you need to summarize what exactly has been done to troubleshoot, and what exactly the symptoms are/where. especially since you supplied wrong information...(what is "a"? accessory on the key switch? irrelevant if so)

 

[kepruno]

I think you need to summarize what exactly has been done to troubleshoot, and what exactly the symptoms are/where. especially since you supplied wrong information...(what is "a"? accessory on the key switch? irrelevant if so)

Agree that ‘a’ is irrelevant. Now I know.
Summary:
1) followed trouble shooting flow chart to -replace distributor sensor - so I did. Cap/rotor and sensor all replaced.
2) low voltage at +terminal on coil while cranking. 12v with key on.
3) ‘I’ terminal at keyswitch has 12 volts while cranking - with all wires connected - new key switch is functioning properly (so was the old one) voltage at power supply to key never drops either.
4) I learned more about 12v systems in the last week than the past 46 years on this rock
5)Appears to me I’m losing power between the key and the coil. I’d like to look at the connections at the kill switch but I don’t know how to get it apart without wrecking it.

 

[Bondo]

5)Appears to me I’m losing power between the key and the coil. I’d like to look at the connections at the kill switch but I don’t know how to get it apart without wrecking it.

Ayuh,........ Is there ignition power(purple) at the big cannon plug, where the boat meets the motor, when the key is "On",..??

Rather that takin' a chance on breaking that switch, any chance you can see the wiring behind that panel,..??
There should be a red, a green, 'n blue wires for the trim,....
a yellow/red wire to the neutral safety switch, 'n back to the harness,....
'n of course the purple wire up to the kill switch, 'n back to the aft harness,....

 

[alldodge]

I should have said every connection except A gets power when the key is turned to start.

Currently have power at the switch (I), not at the coil.

Move purple wire to I connection

 

[Fun Times]

Move purple wire to I connection

Wondering if someone’s been switching wires at the key switch as the colors seem off to me unless I’m going colorblind in my old age ha ha… the colors seems backwards between the I and A.

 

[kepruno]

Wondering if someone’s been switching wires at the key switch as the colors seem off to me unless I’m going colorblind in my old age ha ha… the colors seems backwards between the I and A.

This was where my confusion came from. That picture is the old switch before I took anything apart. The wires are connected the same way as when the boat was running. My problem is not the key switch or the wiring.

 

[kepruno]

Ayuh,........ Is there ignition power(purple) at the big cannon plug, where the boat meets the motor, when the key is "On",..??

Rather that takin' a chance on breaking that switch, any chance you can see the wiring behind that panel,..??
There should be a red, a green, 'n blue wires for the trim,....
a yellow/red wire to the neutral safety switch, 'n back to the harness,....
'n of course the purple wire up to the kill switch, 'n back to the aft harness,....

How do I test the cannon plug? Will it work with the plug apart?

I cannot get behind the panel. I need to take the throttle off. There is no panel, it’s a solid wall

 

[Bondo]

How do I test the cannon plug? Will it work with the plug apart?

I cannot get behind the panel. I need to take the throttle off. There is no panel, it’s a solid wall

Ayuh,..... With it unplugged, is there 12v at the ignition pin,..??
If so, meter the motor side of the ignition pin, to the (+) side of the coil,.....

 

[nola mike]

You need to work your way down the line of connections. Testing resistance across components with them disconnected probably won't tell you much since your problem is only under load. I'm thinking you don't have a ground problem since your red/pu wire maintains 12v and it shares a common ground with purple. You don't need to access the dead man switch directly. Check the purple at the tach when cranking. You can also jump a wire from the I terminal to the tach, which will bypass the switch. If that checks out, back probe (a bit tough) or probe into the wire (avoid this if possible) on either side of the cannon plug.

 

[Fun Times]

This was where my confusion came from. That picture is the old switch before I took anything apart. The wires are connected the same way as when the boat was running. My problem is not the key switch or the wiring.

Take a jumper wire at the back of the key switch and connect terminals B and A, then take another jumper wire and connect to terminal B and touch terminal S (Start) and see if the engine starts normal.

Also right now, when you turn the key to just on (ignition) do the gauges power up? No? Then turn the key to accessories... < It might be further left of key off in some cases... Do they power up now?

When you try jumping B and A, do the gauges power up?

Then if felt needed, Jump B to I and see if gauges power up... Then leave B and I connected, Touch B to S and see if engine starts... Proper testing is often needed by bypassing the key switch as they fail often and in this case appears mis-wired.

Also when time permits, take a new photo of the back of the key switch.... Anything else at this point is just a guess until you know if the switch is working or connected right.
Good luck.

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