Electrics question

Slinky Spring

Slinky Spring

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I have just removed the engine from my boat. In doing so the live to the starter motor and the neutral to the engine casing were disconnected. I now have no electrics on the boat. Can I connect these two leads together to get power back or is it more complicated than that?
 
With the limited info in your post, I guess that there may have been more than one wire on the 'live' starter motor terminal - probably two or more red wires. If so, these are the ones that need joining together but a bit more information would help me avoid the guesswork.
 
I'm fairly sure the power first went when i disconnected the neutral. There only appears to be a single neutral cable attached.
The live connection does have two cables. Should i try to connect these two together?
 
After studying the photos i took at the time it looks as if there were two separate neutrals connected to different points on the body of the engine. On a two battery system is this likely to be the case and if so do I need to connect these two neutrals together?
 
Watch out how you go because some of the wires could be for instrumentation. I would suggest you get someone who knows what they are doing to wire you up or you might end up on fire.
 
On a lot of boats the starter cable is un-fused. Getting it wrong could mean welding the 2 together and burning your boat to the water/ground.

If it is the case that the boat stops working when the engine is disconnected then it is wired wrongly anyway, as the boat electrics will see the full voltage drop including, the cables, while starting.

Please get some help.
 
Positive and negative on a DC system (Live and neutral on AC mains systems)

DO NOT connect any positive to any negative or your are likely to short out your battery.

Before removing your engine you should have disconnected the battery(s) or at the very least switched off the isolator and it/they should remain so until you have taped up (ie insulated) all the positive wires, in fact it would be wise to insulate all the disconnected wires with the possible exception of the negatives.

The wires to the starter motor/solenoid are likely to be:
1. the battery positive connection, that'll be a really thick wire;
2. the output from the alternator, a fairly thick wire on the same terminal as the battery connection
and 3. a thinner wire, to a another smaller terminal, which is the connection from the starter switch (key operated?) to the solenoid.

There will also be connections for warning lights any engine instrumentation, including the alternator charge warning light. Depending on how the system is wired there may be other connections to the alternator.

Normally one would not expect to have to join any wires which have been disconnected from the engine in order to restore power to the general services on the boat.

Without a wiring diagram no one can give you any safe or sound advice via this forum. You should really therefore get some help from someone who knows what they are doing to sort it out for you. The consequences, as already stated of shorting the battery out could be very serious.
 
[ QUOTE ]
Thanks for all the advice. All batteries are out of the boat so I think i will make do with a torch until the engine is back in.

[/ QUOTE ]
If the batteries and engine are both removed that would explain why you don't have any electric power. From your earlier post in which you say there were 2 -ve connections to the engine it's likely that one is from your batteries (a big thick cable) and is part of the starting circuit, and the other (a medium sized cable) is the common -ve for the domestic electrics (lights instruments etc). If you had batteries in and the electrics are dead connecting those 2 -ve wires together would if my supposition were true give you a supply from the battery to the distribution board. Until the batteries ran down anyway.
 
Oh dear .....

I wouldn't advise it !!

Later you say batteries are out of boat ... so where is the power going to come from you want ?

Just a comment based on my engine set-up ...

I have main +ve from battery switch feeds solenoid ... which then is fed to starter. On the same input terminal is a lighter wire that feeds my domestic panel +ve 12v.
Reason for this set-up is that the battery switch then controls which battery feeds systems without having extra wires into the switch.
-Ve lead comes of engine and also domestics fed to common terminal.

So what you describe is similar - but you have to identify more carefully which is which !!
 
Hang on...... I'll just pop to the window I may be able to see the bang from here..... ok ...ready..........................
 
o boy a fire fighter. /forums/images/graemlins/laugh.gif im sory i should not take the mick. but thats funny o well if things go wrong you no whot to do.
i dont serpose there is a photo of the setup or a dirgram to help with, as you will probebly not get a very acurate solition to your problem, sorry for spelling to late in night. /forums/images/graemlins/smirk.gif
 
All of the advice you have been given about the dangers with 12volt welding connections and catching fire is absolutely right. Also it is advisable if you are not sure you should get expert assistance.

If however you wish to continue yourself, you should first contact any of the electrical suppliers in PBO, I am sure they would help you with a suitable wiring diagram.

If you had connected the positive and negative battery cables together and there was no fuse in the circuit there was a high probabillity that the cable/wire would glow red/white hot, and the insulation catch fire.

Therefore I would advise fitting a main fuse directly on the positive terminal of each of the batterys. The only disadvantage of fitting a fuse is that it is possible that the fuse may blow when the alternator is running and this would probably burn out it's diodes. Given the choise between the boat catching fire and loosing an alternator, I know I would go for the Alternator every time.

LSUK sell a fuse holder called a midi (small and neat easily fitted close to the battery terminals)and you can get fuses from 30 to 200 amps, the holders are about £8.00 and the fuses are £2.00 each. If you use an in line fuse holder with a 0.5 amp fuse, and connect that across the terminals of the main fuse holder( as a replacement fuse), this should safegaurd you against the possibility of inadvertant short circuits. All the wires in the boat should be capable of carrying the 1/2 amp, any short circuit would blow the fuse immediately. You should be aware however that if a circuit that required several amps was switched on then that also would blow the 1/2 amp fuse. So you should make sure all circuits were switched off prior to making the connections.
 
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