Starter motor wiring

howardclark

howardclark

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Engine out for fuel tank replacement. Now got to put it all back! But query on how to wire the solenoid for the starter.
The previous owner had a relay fitted because he was having starting problems. It looks as though three wires come from the relay. One to the main + on the starter motor itself. The second appears to go to a bolt on the back of the solenoid and the third to a tag on the back of the solenoid, but the gent who undid it cant find the drawing & we want to be absolutely sure!
First why use a relay?
The solenoid appears to be earthed to the starter motor so what can the tag be for?
Any advice much appreciated
 
sounds like he was having problems getting the solenoid to work, thus a relay to reduce voltage loss to the starter, and a specific earth(neutral) tab on the solenoid to avoid further losses.
 
If you have a normal key starter and decent batteries, can't see why there should be a relay. Boats tend to get more complicated as they grow older/develop/have bits added. Why not simplify a little, remove the relay and activate the solenoid straight from the key start (like most other boats)?
 
Would agree with Talbot seems the most likely scene.

Must confess I have done ze bodge on mine. Starter Button Wiring is old and gets resisitive when hot. Result starts when cold, no start when hot.
Bodge - duplicate starter button in top of engine space, shorter wiring run with full 12 volts hey ho starts every time even when hot.

Yes I know I should rewire after nearly 20 years but .....

Brian
 
Could be faulty contacts in the back of the solenoid.
The wire to starter is to run the motor, the wire to the tag to pull in the pr-engaged, and the one onto the bolt may not be needed, or it may feed a hold in coil in the solenoid.
Berfore refitting get the starter motor checked out at LSUK or similar. Better than throwing the relay away, then finding it was critical for starting.

Brian
 
no the starter motor has its own v. substantial wires. The one betwen the relay and starter motor is about 2 sq mm i.e. would carry approx 20-30amp at most. Main starter cable is about 16 sqmm
 
It not uncommon to relay the starter motor solenoid, this takes the load of the key switch which may not take the current load.

Brian
 
Howard
I'm not sure what engine you have but "normally" on a starter motor you will have a bridgewire or copper plate linking the solenoid to the starter moter. then you have a screwed bolt which takes the mains power from the battery and then a "Lucus" tag which is the solenoid actuator circiut.
You may have more than 1 wire conected onto the screwed terminal to run other boat electrics.

Question?
Although the guy that disconnected the wiring can't remember the sequence - have you looked at the type of connections on the existing wiring i.e. one may have a tag, one a screwed/bored hole to connect to the screwed terminal.

I would have thought that if you have the battery earth (-) bolted on the engine (anywhere). The (+) bolted on the screwed terminal of the solenoid and then take a piece of wire from the + on the battery and touch it onto the tag of the solenoid engine will turn over/start!!!
 
thanks- that all makes sense and I can identify from the ends where the relay wires probably went. There is a bridgewire, but what is the tag on the 'solenoid actuator circuit' for??
 
Howard
The tag has (should have) a single wire conected to it so that when you turn the ignition key to "START" you put 12v (+) on to it, this will then fire the solenoid to engage the internal bridge that allows the full power across the battery terminals and at the same time engages the bendix. As soon as you release the key and lose the voltage it all disengages the dendix and the mains power.

If you have a voltmeter you can connect what you think maybe the 12v wire to one side of the meter and then ground the other volt meter wire - turn your ignition to "start" and you should read 12v. When key released voltage should disappear.

Hope this helps.

Peter.
 
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