1973 Mercury 40hp will not crank

[Jeff P]

Had starter rebuilt and when I connect the starter I don't have 12 volts. With the starter removed I can turn the key on and have 12 volts at the solenoid, connect starter again 12 volts is gone. Any suggestions?

Jeff

 

[Laddies]

Re: 1973 Mercury 40hp will not crank

You have a bad connection in the system

 

[Jeff P]

Re: 1973 Mercury 40hp will not crank

You have a bad connection in the system

Anything specific that I can check? Has new solenoid, new wire harness from motor to switch, rebuilt starter, new stator.

 

[Yesterday]

Re: 1973 Mercury 40hp will not crank

Sounds like the starter motor is a dead short, but if that were the case it would burn up in no time. When the starter is connected, what voltage do you see across the solenoid? Zero? When you say at the solenoid, are you referring to it's input from the ignition switch, or it's output to the starter motor?

In thinking.. how is the battery's charge? If the battery was low the voltage would still likely show close to 12 until a heavy load in which case it would go to near zero while trying to engage the starter. I would put a charger on it for a few minutes and try it, just to see if the solenoid will click. is it even clicking at all?

 

[Jeff P]

Re: 1973 Mercury 40hp will not crank

Yes zero, I couldn't even jump the starter. I then unplugged the harness that leads to the ignition switch. Is this a wire harness issue? It has a new 8 wire harness and everything I've seen for this outboard shows a 6 wire. I thought I saw a way of making this 8 wire harness work, but closed the tab and can't find it now.

 

[Yesterday]

Re: 1973 Mercury 40hp will not crank

The voltage across the solenoid's input from the ignition is unrelated to the hookups to the starter motor. In fact the input feed into the solenoid goes: battery > ignition switch > (possible) fuse > solenoid input. If you are noticing voltage changes at it's input terminal, the loose connection lies at that terminal! There should be zero voltage across it's output to the starter except for when the key switch is in the momentary "start" position.
That circuit goes: Battery > solenoid > starter motor. The solenoid is just a large heavy contact switch, much like a relay. the only thing they share in common is the battery.

 

[Yesterday]

Re: 1973 Mercury 40hp will not crank

Unless suffering from physical damage from some sort of impact, or obvious corrosion, wires don't just stop working.. ever. No it's not a harness issue, unless something burned up since it last worked correctly. A bad starter motor wouldn't effect anything in that sense because it would have to burn up a very heavy gauge wire which is still more or less independent from the rest of your wiring harness.

 

[Jeff P]

Re: 1973 Mercury 40hp will not crank

There should be zero voltage across it's output to the starter except for when the key switch is in the momentary "start" position.
That circuit goes: Battery > solenoid > starter motor. The solenoid is just a large heavy contact switch, much like a relay. the only thing they share in common is the battery.

With the starter removed I get 12 volts across the output of the solenoid with the key in the momentary position. When I connect the starter and turn the key to "start" momentary position I get zero volts.

 

[Yesterday]

Re: 1973 Mercury 40hp will not crank

The either the solenoid is making poor connection (unlikely since it's new) or the battery doesn't enough current to as much as energize the solenoid. One more possibility: Are the battery terminals corroded? if they're heavily corroded or not tightened, you may also see similar effects.

 

[Yesterday]

Re: 1973 Mercury 40hp will not crank

I misread that. so the solenoid is working, just not rolling the starter motor. since the voltage is dropping to zero theres no "open" in the circuit..either the rebuild didn't take or the current isn't ample to run the motor. Im sure it's not the right way to do things but I would insure the ingition switch is off, take a set of booster cables and run one lead from the battery + terminal to the + input on the starter motor, momentarily. That effectively bypasses everything. If the motor doesn't turn, either the battery,or the motor is at fault, period.

 

[CharlieB]

Re: 1973 Mercury 40hp will not crank

............ I would insure the ingition switch is off, take a set of booster cables and run one lead from the battery + terminal to the + input on the starter motor, momentarily. That effectively bypasses everything. If the motor doesn't turn, either the battery,or the motor is at fault, period.

This is the quickest and easiest method of testing a starter.

Also make sure that your battery is charged, then take the battery to your local part store and have it 'Load Tested' to be certain that the battery is good.