charged tinnie

[Dignity]

I started having some problems with the lighting in the tinnie. If I turned on the running lights (red/green) first then the all round white light the running lights would turn off. Now I checked all the circuits with a multimeter and they seemed to be fine, while I was there I decided to try with the positive on the battery and the negative on the tinne and I got a reading of 12.5 volts, is this supposed to happen.

[MyWay]

is your outboard got starter or is it pull start ?

[danryan75]

either your tinny is grounded (intentionally) or you have a short from negative(black) to the boat. if it was a short to red or positive you would be getting a belt when you touch the tinny when you are standing on the ground.

[Dignity]

Myway, has a starter, the motor is a 30hp Merc.
danryan75, I checked that and it is definitely grounded, I had a look under the cowel but could see nothing amiss.

[finga]

one end of the multimeter on the positive of the battery and the other probe on the hull will get 12odd volts.
You said you checked the circuits.
How was this done?
Did you just check the positive or also the negative side of things?
I assume the lights are not grounded to the hull.

Just sounds like a dodgy supply cable or connection in either the positive OR negative wires, terminals, connections, links etc.
The good news is that it should be easy to find with some additional information :)

[MyWay]

Myway, has a starter, the motor is a 30hp Merc.
danryan75, I checked that and it is definitely grounded, I had a look under the cowel but could see nothing amiss.

that is normal to have 12.5 your motor is bolted to boat

Just follow the wires from battery to switch and from switch to lights you will find the problem soon


cheers

[Dignity]

finga, I am not at home at the moment but did disconnect everything and brought the switches with me. I found one switch which seems to be faulty and not have a circuit at all when switched on but dont understand how this affected another set of switches. I had to nearly destroy the box all the wiring was in, the person I bought it off connected it all together then glued and screwed the box together and carpeted the lot. When I get back home I will build a new box so that I can get to the connections and fuses.

The lights were not grounded to the hull but I will check to make sure none of the insulation has worn through anywhere just in case.

[finga]

It sounds like corrosion somewhere on either of the power supply wires to the fuse panel/link or dirty battery terminals to me.
The crook switch may just be another problem that you've already found I reckon.
Easiest way to find it is to turn everything on (so the problem is showing it's ugly little head) and start taking voltage readings (starting at the battery terminals) until you get to the crook spot.
I normally leave one lead of the multimeter on the negative terminal and take readings along the positive wires and, if nothing found, I then leave one lead of the multimeter on the positive terminal and work my way along all the negative wires until problem found.

[Dignity]

finga, did all but the last, never even gave that one a thought although it was hard enough trying to do all of this through a little hole where the main switch was, this was was when I gave up and destroyed the whole box to pull it all apart late at night and threw it in my kit bag. Starting all over and building a proper accessable box will probably rectify the problem, hopefuly.