voltage drop between battery and dash gauge

[Rouscy]

Hello,
I was having trouble cranking my mercruiser 3.0l engine like the battery didn't have the power to turn the starter.So I bought a new battery but problem still there.I read 12.8V on my new battery with my portable voltmeter and 12V on dash gauge (before cranking).Even with a new battery the starter turns slowly just enough to start the engine. Where could be the problem? I also have a battery isolator

regards
Andy

 

[H20Rat]

Re: voltage drop between battery and dash gauge

gauges only read voltage, not resistance. You need to start checking things out with a multimeter on resistance, I'd be willing to bet you have a bad cable or ground somewhere in there. Check for any loose crimped connections, or any corrosion.

 

[coastalrichard]

Re: voltage drop between battery and dash gauge

Also check the terminal connections at the battery and at the starter. Each should be bright and clean...no corrosion...and tight!

 

[jopes]

Re: voltage drop between battery and dash gauge

Also check the terminal connections at the battery and at the starter. Each should be bright and clean...no corrosion...and tight!

If the terminals are all clean and tight then your ignition timing maybe too far advanced.

 

[jopes]

Re: voltage drop between battery and dash gauge

ANother thing you can check is to put a meter on the battery and have someone start the engine watch the battery voltage. Then go to the starter and do the same again.

Be sure to hook up muffs or put it in the water when starting.

 

[bruceb58]

Re: voltage drop between battery and dash gauge

gauges only read voltage, not resistance. You need to start checking things out with a multimeter on resistance, I'd be willing to bet you have a bad cable or ground somewhere in there. Check for any loose crimped connections, or any corrosion.

Measuring resistance with a multimeter is pretty much a losing battle as a very slight added resistance(very hard to measure) will add up to large voltage drops. Best way is to measure the voltage drop between two points to see where the drop is occuring when a load is on the circuit.

For example, to see if the voltage drop is in the ground side or the positve side up to your dash, measure voltage between the positive side of your battery and positive bus of your dash fuse panel. Do the same for the ground. If one has a large voltage drop, that side is where you need to do more investigation.

If your engine is cranking slow, measure the voltage drop between your battery and the positive lug of your starter. Likewise measure the voltage drop between the negative post of the battery and the engine block. The drops should be equal. if one is appreciably more than the other, that is the side that has the resistive connection.

 

[burp]

Re: voltage drop between battery and dash gauge

^
+1 regarding Bruce58 reply