converting from ammeter to voltmeter

ScottinAZ

Master Chief Petty Officer
Joined
Jun 25, 2009
Messages
831
ok, boat is a 1980 vintage galaxy with Mercruiser 120 running gear. I have manuals for the system. I have an unnatural hatred for ammeters, I just dont care for the idea of a single wire running the length of the boat, through the gauge, and back to the battery. too much length for something to happen to it, or the gauge to go belly up, and then you lose all electrical.

I am looking at manual #3 section 3F pages 3F5 and 3F6 for the schematics between the two systems, ammeter or voltmeter.

Seems the change is where the orange wire goes on the engine side, with the ammeter, it goes from the alternator to the cannon connector to the gauge, and at the ammeter (page 3F66) joins with the red/purple wire there, and proceeds back to the engine harness to the slave starter solenoid and then to the battery.

With the voltmeter, orange wire goes from the alternator to a junction point on the red/purple wire between the circuit breaker and the alternator itself providing the orange wire a path to the battery.

What is the general consensus on the usefulness of an ammeter vs voltmeter? I know what I prefer, and what the boat is currently wired for. If there is a pressing reason to keep an ammeter on the boat, Ill entertain it (but wont like it)
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,054
Amp mostly started with Generators, then switched to Volts when the Alternator came out. Would take volt over amp any day.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,540
To remove ammeter, join the two wires together

Remember all the power goes thru the ammeter now. If you intend to add a load or bigger alternator, you will need to increase the wire size.

A volt meter goes between that junction point and ground
 

ScottinAZ

Master Chief Petty Officer
Joined
Jun 25, 2009
Messages
831
To remove ammeter, join the two wires together

Remember all the power goes thru the ammeter now. If you intend to add a load or bigger alternator, you will need to increase the wire size.

A volt meter goes between that junction point and ground
thats about what I thought.

plan right now is to leave the engine side of the harness intact, as designed and built by Mercruiser. Its still wrapped and in great pristine condition. No sense cutting into this. The boat side of the cannon plug is already loose wire. I will take the orange lead from this side, cut it back and attach it to a battery cut off switch in the battery box. (this effectively attaches the orange alternator output lead to the battery, to charge said battery). I will then take the red/purple lead that was the "other" side of the ammeter leg, add a maxi fuse holder in the battery box (for safety) and use that lead to power the front dash of the boat. (becomes a large 10 gauge feeder essentially). all wires are therefore protected, and/or kept as short as possible limiting the "unfused" sections of 12v power leads. This should also follow "the intent" (if not the actual execution) of the Mercruiser schematics.
 
Top