Ignition switch failing?

[thomis]

1992 Stingray bowrider, Mercruiser 3.0...
Sometimes when you turn the key there is nothing. No noise or sound, no click, just nothing. After turning the key a few times it fires right up. Sounds like the starter is strong. The battery has been tested and is good. The alternator is charging it, with full load and accessories on I'm getting 14.5 volts. It doesn't struggle to turn over. It really sounds like the issue could be right there at the key, like the actual switch? Is there is a way to test this?

 

[achris]

It may be the switch, but I would also check the 20A fuse that feeds the switch. I've seen corrosion on the end of the fuse that has caused exactly the symptom you have.

Chris...

 

[nola mike]

It may be the switch, but I would also check the 20A fuse that feeds the switch. I've seen corrosion on the end of the fuse that has caused exactly the symptom you have.

Chris...

Huh, you mean like this? Was tracking down a voltage drop this weekend. Still got 0.25v across the switch, but this cost me almost 1v with no load

 

[achris]

Huh, you mean like this? Was tracking down a voltage drop this weekend. Still got 0.25v across the switch,

Bingo!

3AG glass fuses in boats? What could possibly go wrong?

Get yourself a mini blade fuse and holder and replace that POS.

but this cost me almost 1v with no load

Which will be all (12v) of it under load.

Chris.......

 

[1960 Starflite]

It may be the switch, but I would also check the 20A fuse that feeds the switch. I've seen corrosion on the end of the fuse that has caused exactly the symptom you have.

Chris...

Chris nailed it. I had the same problem. Replaced switch, didn't solve anything.
Put a volt meter + on switch side of fuse, read 12.5 volts. Switch on run, read 11.8 volts. Switch to start position, read 2-3 volts.
Wiggled fuse with small screw driver then it worked. Removed fuse, cleaned fuse holder and fuse, problem solved.
Cleaned all the contacts in fuse box while I was there.

 

[achris]

Removed fuse, cleaned fuse holder and fuse, problem solved....

For now. 100% guarantee it will happen again.

Buy a simple mini blade fuse holder and 20A fuse and cut the glass fuse holder out. Solder in the new holder and use your boat with the confidence that those glass fuses won't spoil your day ever again. (Fuse holder)



Chris.

 

[thomis]

Finally got behind the dash to look at the wiring to the switch. It looks pretty clean.
There is a
1) yellow wire with a red stripe;
2) pink wire with a purple stripe and
3) purple wire going to the ground safety cutoff switch.
The markings on back of the switch are "B" on one side and "I" and "S" on the other side.
Regarding checking the in-line fuse. I can't locate this. Where might the fuse be located?
Here are some pics:

 

[dubs283]

the ignition fuse is most likely at the fuse panel not in-line, i think an in-line fuse was merely suggested for you

B = battery constant 12 volts
I = ignition, 12 volts in the "run" position
S = start, 12 volts in the "start" position

easy to test with a voltmeter

 

[Bt Doctur]

ign safety cut off does NOT go to a ground

 

[achris]

And that is not a standard Merc ignition switch. Merc ignition switches have the 3 wires coming from them soldered to the switch body, not spade connectors. Follow the wire that goes to the B terminal (red/purple) back. It should have a fuse in it somewhere.

 

[thomis]

I used a jumper on the slave solenoid and it started like a champ, that rules out the starter being bad. Should I just go ahead and replace the slave solenoid AND the ignition switch? Makes sense to me...
Thanks to all of you, I appreciate it greatly.

 

[achris]

And what if it's not the switch or the solenoid, but something else? I'd do the diagnostics properly, but it's your money....

 

[thomis]

I found the 20 amp fuse, looks fine. Not loose, no corrosion. Just received the new switch. I'll replace it and report back..

 

[thomis]

It was definitely the switch. The new brass switch works great. Starts without hesitation. The old switch had spade connectors, I think they are not as secure as the ring terminal connectors on the new switch.

 

[achris]

I'd still replace that glass fuse....

 

[thomis]

I don't have a glass fuse? My fuses are:

 

[achris]

That big white fuse holder in the middle of the picture, open it up and look at the fuse inside. It's a GLASS 3AG fuse...