Mercury 150 start with solenoid not key

[lunasuenos]

2002 150 saltwater series non EFI. Will start if you short with a screwdriver across the solenoid but does nothing with igition key.
First thought bad solenoid replaced and same result, replaced ignition key nothing same result and by passed the shifter kill switch. Still nothing. When ignition key is turned to start voltmeter in dash shows a discharge like a short. If you start it by jumping the solenoid motor runs perfectly. This motor is on a 19 foot trophy.

Any ideas?

 

[Silvertip]

Re: Mercury 150 start with solenoid not key

You do NOT have a short. What you probably have is a blown fuse on the power head. Here is what it looks like on a 75 HP Merc. When a "voltmeter" goes to zero, it is an open circuit which is normal when you turn the key to START. Power returns to the gauges when the switch goes back to RUN. The fuse is in the black holder just above the solenoid. If that's ok, then there is a wiring issue between the keyswitch and the engine. Disconnect and reconnect the large harness connector at the engine. A little corrosion in that plug is enough to create an open circuit.

 

[lunasuenos]

Re: Mercury 150 start with solenoid not key

Thanks for the response Picture helped. Here is a update. Running a wire directly from "S" position on key to the solenoid works. Now starts with the key. Did find fuse block in motor has 3 fuses. Per manual it shows (3) 20 amp fuses. However the block has (2) 30 amps and (1) 20 form left to right. None were blown. Motor is used so I am wondering if having the higher amp fuse has caused a wire to burn? What else would be on this circuit form key to solenoid? Any other motor functions or alarms that may now not be working. I will need to add a fuse to the by pass wire we have run I guess. Any comments will be appreciated

 

[Silvertip]

Re: Mercury 150 start with solenoid not key

If there were no issues with wiring then a larger fuse than specified is not a problem. However, if there is an issue with wiring, such as a screw driven into the main harness, that can create a short and instead of the fuse blowing, the wiring burns because it is not capable of handling that amount of current. In other words the becomes the weak link in the chain rather than the fuse. There should be nothing else in that circuit except the solenoid so perhaps it is drawing too much current. To check the existing line, disconnect it from the "S" terminal on the switch and at the solenoid. Now measure from either end of the wire to ground. It should show open circuit. If it shows continuity, that wire is indeed shorted somewhere along its length. Then measure continuity end to end. It will probably show that it's open meaning the wire is physically broken somewhere along it's length.