Engine Will Not Turn Over

[JDusza]

Hi. Working on an oil injected Mercury 40 hp. Yeah, one of those...
It will not turn over to start.
1 I have 12+ volts feeding the helm ignition switch, but only 3 volts coming out feeding the starter relay when the key is turned to the start position. Thought I had a bad switch so I replaced it. New switch gives same results.
2 Voltage on the red wire coming to the ignition switch from the starter relay fat lug, which is fed directly by the battery, has 12+ volts. If I bypass the starter switch and contact this 12+ volts to the starter relay yellow and red, the engine will not turn over.
3 If I take 12 volts from the battery with a jumper and touch the starter relay yellow and red at the helm, the engine turns over fine.
4 Why is the 12+ volts that I measure at the ignition switch not transferring power to the starter relay with the turn of the key?
5 Bad ground?
Thank you,
J

 

[Chris1956]

Bad power cables feeding both the starter solenoid and the ign switch.

If you can jumper just the positive to the starter and she cranks, the ground is likely fine. Check the entire battery cable length with fingers looking for corrosion under the insulation.

 

[JDusza]

Yikes!
And both of those are in the main harness. He he he he .....
Thank you,
J

 

[QBhoy]

In gear switch or lanyard maybe ?

 

[airshot]

Just went thru a similiar issue on my 1992 40 hp classic. After a thorough and carefull search, I did find a number of corroded connections and one very teeny, tiney little pin hole that was grounding onto a ground screw. That hole was thru a wrap around a group of wires, about the size of a pin head. Re wrapped with sime geavy gorilla tape, cleaned the corroded areas with a small brass brush, brushing until nice and shiney. Took every connection apart to check them. Spent pretty much a whole day cleaning abd tightening....but...everything now works great !! Multiple poor connections can create a big headache !!