7.4 alternator ?

ericcarr2000

Ensign
Joined
Mar 19, 2010
Messages
903
I will be replacing the stock alternator on my 290 7.4 motor. My question is will a standard 1 wire alternator do the job? I just want to ask before having to climb into the engine compartment is all.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
I will be replacing the stock alternator on my 290 7.4 motor. My question is will a standard 1 wire alternator do the job? I just want to ask before having to climb into the engine compartment is all.

So long as you don't have an isolator or ACR in line between the output of the ALT and the battery.

Now for the three wires you won't be using. One is black and that's just a ground, one is red/purple and the other is purple. Both wires have 12V on them when the engine is running, Red/purple (all the time) and Purple when running.

My opinion, I would not change it

Edit: not change
 
Last edited by a moderator:

ericcarr2000

Ensign
Joined
Mar 19, 2010
Messages
903
Ok, I guess I'm asking is will I be safe if I order a 1 wire alternator or what kind do I need to?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Why would you buy a one wire alternator when a 3 wire is actually better?

And why are you replacing your alternator? Is it not working?
 

ericcarr2000

Ensign
Joined
Mar 19, 2010
Messages
903
I'm repowering her with a mildly built 454 and was thinking of just replacing it with a nice chrome one. I can't remember if the one that's on there now is a 1 or 3 wire though.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Just realized I left the "not" out of my prior post. I would not change to a one wire. You should have a three wire currently installed
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Standard 65 amp is all you need unless your going to put in a mega stereo system and lights with several batteries
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Agreed, what are you operating that you need a bigger alternator?
 

ericcarr2000

Ensign
Joined
Mar 19, 2010
Messages
903
Nothing really, I just have the 2 batteries. 1 for the deep cell battery and the other one for the lights & such stuff.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Just keep your present alternator then. Spend the money on an ACR.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
What's a acr?

Automatic charge relay, turns on when the engine is running to charge both batteries. This or an isolator will do pretty much the same thing (OK the ACR is better by .10V).

My opinion, just keep what you have and do nothing
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
ACRs are also smart so that you aren't charging a battery that has failed so that your good battery continues to get charged. I have ACRs on both my boats and on past boats.

Diode isolators have voltage drops from around 0.4V to 0.7V. Only way to get around that is to remote sense on one of the batteries.

https://www.bluesea.com/products/761...12_24V_DC_120A
 
Last edited:
Top