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rem_pss308
06-01-2005, 01:34 PM
I recently added a second battery, and isolator. I am replacing the old alternator with one that puts out 100 amps. My question is will I need to upgrade any of the wireing coming from the alternator to a larger size.

Engine Nut
06-01-2005, 03:20 PM
I recently added a second battery, and isolator. I am replacing the old alternator with one that puts out 100 amps. My question is will I need to upgrade any of the wireing coming from the alternator to a larger size.

You will absolutely have to change the size of the wiring. According to USCG wiring chart a 100 Amp circuit with a conductor length if 10 feet (5 feet on the + side and 5 feet on the negative side) you would need 4 gauge wire. For 15 or 20 feet you need 2 gauge and for 25 feet you need 1 gauge wire.

Engine Nut

BriEOD
06-01-2005, 06:02 PM
Hey Mike,

Where did you get the alternator? Is it a marine alt? How much? Gracias.

rem_pss308
06-01-2005, 08:57 PM
Hey Mike,

Where did you get the alternator? Is it a marine alt? How much? Gracias.

Off e-bay.com I searched for Marine alternator. Yes it is marine.
$99.00 after shipping.

Talked to the guy and he says it will put out about 55 amps at idle.

aprgriggs
06-01-2005, 09:02 PM
does putting on a bigger alternator reduce the engine power or preformance?

rem_pss308
06-01-2005, 09:02 PM
You will absolutely have to change the size of the wiring. According to USCG wiring chart a 100 Amp circuit with a conductor length if 10 feet (5 feet on the + side and 5 feet on the negative side) you would need 4 gauge wire. For 15 or 20 feet you need 2 gauge and for 25 feet you need 1 gauge wire.

Engine Nut


Tell me if I have this right. I need to change the wire from the alternator to the battery with the size you said above. I will also have to upgrade the breaker too wont I?
Any ideas where I might get a 100 amp breaker for this. I will check SKidim, and west marine.

Or are there other wires I will have to change also.
I am thankful for the help because I have never done anything like this. But I am getting very educated.

rem_pss308
06-01-2005, 09:05 PM
does putting on a bigger alternator reduce the engine power or preformance?

I read on another forum that it does lug the engine more. It was said that one over 150, would need a serpintine belt, because of the load. So I am sure it would lug the engine a little.
I am sure someone else can expand more on it.

Engine Nut
06-01-2005, 09:45 PM
Tell me if I have this right. I need to change the wire from the alternator to the battery with the size you said above. I will also have to upgrade the breaker too wont I?
Any ideas where I might get a 100 amp breaker for this. I will check SKidim, and west marine.

Or are there other wires I will have to change also.
I am thankful for the help because I have never done anything like this. But I am getting very educated.
You shouldn't have to increase the size of the breaker. Just ron the pos lead from the alternator to the battery stud on the starter and the ngound directly to the engine block. You shouldn't have to increase the size of the breaker on the engine harness as it is only there to protect the harness. Your added accessory load should come directly from that battery to the load. That accessory "bus" must of course be protected by its own breaker.

Engine Nut

jt76ss
06-01-2005, 09:50 PM
I changed out my alt with a gm one wire that i had a local alt shop custom built to 125 amp's and did not change any wires just took off the ones i did need any more. been running it for a year now with no problems and it does not affect performance!

6ballsisall
06-01-2005, 10:07 PM
Rem, keep us in the loop on how that goes. I am thinking about upgrading my old Alt.

JDK
06-01-2005, 10:48 PM
and did not change any wires just took off the ones i did need any more. been running it for a year now with no problems

Dude, the first time your battery is really really run down, but still manages to start the engine.......and you immediatly go on a high rpm cruise, you are going to find out what burning wire smells like. :steering:

BriEOD
06-01-2005, 10:50 PM
Jeff you keeping the 86'?

erkoehler
06-01-2005, 11:30 PM
Rem, keep us in the loop on how that goes. I am thinking about upgrading my old Alt.


I thought you were selling?

rem_pss308
06-02-2005, 10:07 AM
You shouldn't have to increase the size of the breaker. Just ron the pos lead from the alternator to the battery stud on the starter and the ngound directly to the engine block. You shouldn't have to increase the size of the breaker on the engine harness as it is only there to protect the harness. Your added accessory load should come directly from that battery to the load. That accessory "bus" must of course be protected by its own breaker.

Engine Nut

The accessories you are talking about: What do you mean by " BUS"

Here is what I have.
I added a second battery. on the second battery I have all my toys. The radio, Two amps, Tower lights, and ballast pumps. all listed have there own wires run from the battery. ( 6 gauge ) positive, and negative. They are fused at the battery. is this the accessories you talk about?

The alternator has one wire. the ground goes through the frame to the engine block, so I should only have to increase the the wire going to the starter. Correct?

Engine Nut
06-02-2005, 01:30 PM
The accessories you are talking about: What do you mean by " BUS"

Here is what I have.
I added a second battery. on the second battery I have all my toys. The radio, Two amps, Tower lights, and ballast pumps. all listed have there own wires run from the battery. ( 6 gauge ) positive, and negative. They are fused at the battery. is this the accessories you talk about?

The alternator has one wire. the ground goes through the frame to the engine block, so I should only have to increase the the wire going to the starter. Correct?

A "BUS" would be a large diameter wire that would run friom the battery to the front of the boat for connection of accessories etc. Since you have run all of your individual accessories directly to the battery, you are not utilizing a "BUS" connection. If you have a one wire alternator that grounds directly theough the case to the engine block, you will only have to increase the size of the wire going from the alternator to the starter.

Engine Nut

6ballsisall
06-02-2005, 01:53 PM
Jeff you keeping the 86'?

Long story, I'll post tonight

rem_pss308
06-02-2005, 04:48 PM
Thanks Engine Nut. You have cleared up a lot for me.
I wish I had run a bus. But was not sure if it would be enough.

I talked with Vince at Skidim.com today, and he advised that I run the wire from the alternator to the battery. He said it keeps it from running through the boat wireing harness in case something happens.

ALso thanks to everyone else. Again the board has helped a lot.
I will post when I am through with the install, and get results.