Rage

It is a 2005 Mercruiser 496HO wiring harness to dash where purple power wire (switched battery power downstream from ignition switch) that provides power to dash gages etc. is about 1 volt less than actual battery voltage. Is this normal or what should it be?

Blueabyss

What is the Voltage?

Rage

Only measured actual voltage engine off . Battery 12.5v dash 11.5v.

Blueabyss

Do you keep it on charge all the time. Does the battery drain down over a few days if switch is left on. Last is the voltage at the battery and at the dash measured with a digital volt meter. Same meter on Both?

Chris

sutphen 30

start cleaning the grounds,may want to bring a good ground from the battery up to the dash and remeasure,if good,bad ground,if bad,re measure but switch wire to +side of battery and measure from helm ground point.

BUP

iTrader: (9)

Improper sized cables and wiring ? ---- to small gauge cables / wiring for the length of runs cause resistance --- resistance causes voltage drops. Corrosion does the same for all electrical connections

POOR GROUNDS - or loose ground connections

anything spliced in the wiring harnesses like add on electronics or power equipment ?

weak batteries / load test your batteries - a fully charge battery is 12.7 to 12.8 Volts.

bad connections - wing nut connections are improper connections for marine apps. All marine engine oems have put this info out for the past 20 years.

corrosion on terminals / lugs and connections and or corrosion has wicked its way up the cables / wiring under the sheathing ? Again corrosion will cause resistance and resistance cause voltage drops.

Tinkerer

Like I said on the other site the wiring on boats is undersized for the load. The power wire and ground are no where near large enough and that causes voltage drop.
Like others have said check all connections. turn on something that draws a few amps and then check every connection between the battery and the load for voltage drop. then follow the ground wire all the way back to the battery.
At every connection you will see a SMALL voltage drop. This is normal. IF you see more than .2 to .3 volts drop than You might want to redo the connection. The ignition switch is a big candidate for voltage drop.
AND if you really want to help the problem run a NEW red and black wire from the source and ground terminal to the dash that is half the gage size as the original wire.

Rage

Thanks for the detailed diagnostic suggestions.

Additional info. The red power line voltage at the fuse panel located at the dash that services accessories not controlled by ignition switch is essentially identical to battery volts. Its only the purple wire voltage which is sourced from the ignition switch that is the 1 volt lower.

I am primarily wondering if anyone knows if this is normal with the Mercruiser wire harness system with the ignition switch, kill switch, neutral switch, etc. circuits and its wiring sizes as provided.

BUP

iTrader: (9)

how are you testing the 1 volt drop ? with a volt meter ? And no it is not normal to a 1 full volt drop across circuits / components and so forth. The same goes for voltage testing from battery to starter - starter to alternator - the voltage should read the same as a example or a very very slight voltage drop.

Rage

Digital voltmeter with (-) connected to battery terminal. Same unit used for all measurements.

OK. Thanks for the help.