wiring question

[debydete]

Why do the main power cables, to my outboard, show a continuity reading even though they are disconnected from the battery and all utilities(lights,bilge,etc) have been turned off?
This is an educational question. There is no short in my engine and it works fine. It just seems to me, when hooked up, the battery would run down if there's continuity in the circuit, but it doesn't.

[boscoe99]

I am having a tough time imaging your specific configuration.

Continuity within a wire is completely independent of whether or not the wire is connected to anything. If in good condition the battery cables will have continuity whether they are connected to a battery or the motor. Could be either end or both.

If a wire has continuity then current can flow through it. If there is no continuity there will be no current flow.

Let us assume the cables are good. They are connected to the battery at one end and to the motor at the other end. There is continuity from the end of one battery cable back to the battery, through the battery and through the other cable back to the motor. But no current will flow because the circuit is not complete. The battery will not run down.

Now press a trim switch. Current will now flow from the positive battery cable (conventional currently flow theory) at the motor to the trim switch motor, through that motor, back to the ground battery cable on the motor, and then on to the battery. Hold the switch closed for long enough and the battery will go dead.

Does any of this answer your concerns?

[debydete]

I don't think you understand what I'm asking.
Imagine the battery is removed. You now have the two cables going to the motor. If I place ohmmeter leads on the ends of the two cables, that were connected to the battery terminals, the ohmmeter gives a reading.
I always assumed that the hot cable, on its way to the starter and utilities, went thru switches so that there would be no continuity to the ground cable until a switch was closed and until then an ohmmeter would show infinite resistance, i.e. an open circuit.
I would add, this is not unique to my Yamaha. This all started when we thought we had a short in a friends Johnson because we were getting the same reading as described above. That's when we decided to try the meter on my motor, which we knew didn't have a short.

[boscoe99]

I did not think I understood your original question either. You have confirmed it.

What specific model of motor is in question.

Your original question appeared to relate to continuity. Now you are talking about using an ohm meter. Is your question about continuity or about resistance?

Communicating is hard.

[debydete]

My Yamaha is a 2013 70 hp 4cy. My friends Johnson is a 75 hp 2cy, about 12 yr. old.
Yes, I use ohmmeter reading & continuity interchangeably. If an ohmmeter gives a reading, other than infinity (needle doesn't move), then the circuit is continuous having a certain number of ohms resistance. If the needle doesn't move then there is infinite resistance in the circuit as would occur in an open circuit. Is that not correct?
So I'm saying my motor circuit, and my friends, shows an ohmmeter reading, indicating a continuous electrical circuit between the hot cable and the ground cable, even though the battery is removed and all switches are open.

[dubber]

What value does the ohm meter read? Continuity usually implies a very nominal resistance such as a few ohms max. Infinity implies that the circuit is open. Anything else implies there is some sort of a resistive load but that is not continuity.

[debydete]

I honestly didn't pay attention to the ohms value.
So say there was 500 ohms. I still don't understand why there would be any resistive load.
That might not be the typical definition of continuity , but it would still pull current from the battery, although I suppose not much.

[dubber]

Try to get your hands on the wiring diagram for your motor and see what is up. I find that leaving my battery connected all the time leads to it draining quicker than if I disconnect it when sitting for weeks.

[debydete]

Your comments have been very helpful in getting me thinking. If the resistance was very high, like 500 ohms, it might be normal for some of the electronic parts, like in the voltage regulator, to be connected that way. When my friend brings his meter in a few days I'll check the ohm reading.
I did some calculations (I know quite a bit about basic electricity) and 500 ohms would only draw .024 amps from a 12v battery, and at that rate a typical 80 amp-hr battery would last several months before going dead.
I remember the ohmmeter needle only deflected about half way, but I don't know what scale the meter was on.
Thanks for your imput. Now I'll check the resistance value and also try and find the wiring diagram.

[dubber]

Yup. Ohms law! It doesn't take much but a battery will slowly drain when connected. Be sure to share back what readings you see for this to live forever on the internets for the rest of us

[Jerry Bailey]

My motor cables would show small spark when when first connected to the battery(same thing you are saying with ohmmeter reading). Some said electronics or stator would do this but was very small or was just an initial charge. It still bothered me and so I put a simple cut out switch between battery and motor. It mounts on battery and has a T-handle that u just turn. I suppose if u kept your battery's on a charger all the time it would not matter but I just did not want current to my motor when not in use.