Low Voltage to the Ignition Switch

[nola mike]

I havent attacked the fuse yet, only because t's really difficult to get to, and I'm not a young, or limber (or small) man anymore, but I'm going to replace it soon.
My thoughts on why it worked, remembering i am, let's say, an advanced novice on electrical. First, it worked to jump anywhere into the starting circuit. Since it was low voltage, not no voltage, adding a 12v source is like a booster. I basically bypassed the fuse from a different clean circuit, kinds like through the back door. I fed it from the main 12v block at the helm, which is straight from the battery. I dunno...but it works. It will only be temporary and the fuse will be replaced well before the busy boating season is back, but we do use our boat year round.

However 100% of the juice to the starter comes directly from the battery before hitting that fuse. You're bypassing the ignition circuit but any back feed would still need to pass through the fuse. As long as you have enough volts in the ignition circuit to activate the slave (and then enough volts from there to activate the main solenoid), cranking speed is still dependent on the main battery cable to the starter. And battery ground. But I guess I can't argue with success.

 

[Danno1966]

I get what you're saying.
But the 12.6 volts from the battery turns into 11.7 v on the other side of the fuse, all the way through the Cannon plug, to the slave solenoid, the engine circuit breaker, to the ignition switch. I'm just feeding that circuit 12.6v.
It works, but I agree, confusing as to exactly why. I can even hear the fuel pump is louder! Starting doesn't suck the house lights nearly as much. Guages all read perfect.
In fact, the dash voltmeter barely recognized any voltage with the key on, now it's reading full 12V. I actually thought the guage was bad. With the engine running I'm reading 14+v on my digital guage, when it would barely break 13v before.
What would you expect from a degraded fuse if it wasn't allowing full voltage through? What would be the expected symptoms?

 

[nola mike]

I get what you're saying.
But the 12.6 volts from the battery turns into 11.7 v on the other side of the fuse, all the way through the Cannon plug, to the slave solenoid, the engine circuit breaker, to the ignition switch. I'm just feeding that circuit 12.6v.
It works, but I agree, confusing as to exactly why. I can even hear the fuel pump is louder! Starting doesn't suck the house lights nearly as much. Guages all read perfect.
In fact, the dash voltmeter barely recognized any voltage with the key on, now it's reading full 12V. I actually thought the guage was bad. With the engine running I'm reading 14+v on my digital guage, when it would barely break 13v before.

Yes, all of these are symptoms are low ignition circuit voltage, which it looks like is coming from (at least) the back side of that fuse. Again, once the slave solenoid is activated, the ignition circuit is taken out of the equation for the starter.

What would you expect from a degraded fuse if it wasn't allowing full voltage through? What would be the expected symptoms?

Your symptoms at the fuse are probably from poor connections at the fuse rather than the fuse itself. I've taken them apart, they're pretty robust in terms of keeping water out of there. See my post #16. I think you probably have 2 issues, both of which could be traced to poor connections at that fuse/starter. What happens if you jump the slave?

EDIT: I'm a bit confused now reading through your posts. Are you having a problem with starter cranking SPEED, intermittent cranking when you hit the switch, or just the symptoms from your last post?

 

[Fun Times]

Going to the 90 amp fuse on the starter...had 12.6 v to the battery (#1) but only 11.7 on the back side (#2).

In reading the quote above, does your boat have a battery switch and 2 batteries?.. (Battery 1, battery 2, All batteries)

if so, thinking you may have a bad cable to one of the batteries too…

 

[dingbat]

My money is on resistance (corrosion) between the starter post and the fuse tab

check resistance between the starter post and the output of the fuse

 

[Scott Danforth]

I'm going with multiple badd connections. Remove ever connection from the matter to the helm one at a time. Take 150 grit sand paper, and clean everything until it's shiny enough for your mother in law to eat off. Then seal that connection with a marine electrical varnish. Then move on to the next connection . If any cables are crunchy under the insulation, replace it

The corrosion shown on the B terminal stud and the fuse would be enough to drop voltage. If all the connections are just as funky, that would explain the symptoms you are seeing

 

[Bondo]

The corrosion shown on the B terminal stud and the fuse would be enough to drop voltage. If all the connections are just as funky, that would explain the symptoms you are seeing

Ayuh,...... Ditto,.... Start at the battery, 'n both ends of both battery cables,.....

 

[cyclops222]

I read your first post. Also the age of the boat. Sure sounds like the boat was FLOODED at least 1 time. To have so many and much voltage drops everywhere. Fuses and WIRING. DO NOT ever corrode. If never flooded.

 

[Lou C]

As much as it pains your body you must get down in the bilge & up close & personal with the starter terminals battery cables & engine grounds. You’d be surprised at what you find. And the engine doesn’t have to be flooded, simply moisture in the air and temperature swings cause condensation which causes oxidation & corrosion. Clean and moisture proof! Condensation due to moist air & falling temps cause far more corrosion & oxidation than people realize….
I kept part of an old rear bench seat for my boat that I put on the deck to lie on when doing these jobs.

 

[Lou C]

an old seat cushion to lie on when changing a starter makes it less painful.
also when changing that impossible to reach steering actuator

 

[Fun Times]

View attachment 404217
an old seat cushion to lie on when changing a starter makes it less painful.
also when changing that impossible to reach steering actuator

That’s a sign of age….




Smarter!