Engine ground question

charliebabb

Cadet
Joined
Dec 6, 2012
Messages
17
Hey guys, I was having some problems finding a ground on my boat. What I did was I connected one end of my multimeter to the negative of one of my batteries and touched around on the boat and found continuity on the engine block. That's what I was expecting. After that I had realized that I had the multimeter connected to the positive post. So I'm getting continuity on my engine block to my positive post on my battery. This can't be right?
Any suggestions?


Thanks for the help
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Engine ground question

Sounds like you had your meter measuring voltage rather than resistance, charlie. That would be any boat in my experience. On the other hand there might have been boats wired for positive ground, rather than negative.

Maybe your Hatteras is wired for a positive ground.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: Engine ground question

So I'm getting continuity on my engine block to my positive post on my battery. This can't be right?
Any suggestions?
Its not really a valid measurement. An ohm meter puts out a slight voltage and measures the drop on that voltage. Resistance measurements can only be done on circuits where voltages won't influence the resistance measurement.
 

hrdwrkingacguy

Petty Officer 1st Class
Joined
Mar 9, 2010
Messages
368
Re: Engine ground question

Its not really a valid measurement. An ohm meter puts out a slight voltage and measures the drop on that voltage. Resistance measurements can only be done on circuits where voltages won't influence the resistance measurement.

True...My meter beeps at me in a very condescending way when I measure ohms on a live circuit...:eek:
 

hrdwrkingacguy

Petty Officer 1st Class
Joined
Mar 9, 2010
Messages
368
Re: Engine ground question

I use this for a lot of stuff at work and around the house and boat...A Fluke usually wont go "poof" unless you out of the voltage range...:eek:
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Engine ground question

Hey guys, I was having some problems finding a ground on my boat. What I did was I connected one end of my multimeter to the negative of one of my batteries and touched around on the boat and found continuity on the engine block. That's what I was expecting. After that I had realized that I had the multimeter connected to the positive post. So I'm getting continuity on my engine block to my positive post on my battery. This can't be right?
Any suggestions?

Thanks for the help

Look at it this way -- if you had the meter set to DC Volts rather than Ohms, it would have measured 12.6 volts provided the battery was fully charged. You don't have a problem.
 

wrench 3

Commander
Joined
Aug 12, 2012
Messages
2,108
Re: Engine ground question

Yep, you cant beat a Fluke.

Most of the boats I've had came with every thing wired back to the battery negative. It makes quite a mess and is a hassle when removing the battery for winter storage. So I install a ground buss in a central location and run one ten gauge wire to it. the ten gauger will handle all the usual accessories, just don't hook up a 600 watt inverter or something.
 

joed

Lieutenant Junior Grade
Joined
Sep 28, 2002
Messages
1,132
Re: Engine ground question

If you had some device turned on then you could get a reading from positive to the engine block on ohms scale. It could have even been through the charging stator coil.
 
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