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Author Topic: Charging trouble on a 5.7 alpha 1  (Read 3650 times)

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Offline ChfBrianB

  • Brian Bergstrom
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Charging trouble on a 5.7 alpha 1
« on: July 04, 2012, 07:14:35 AM »
Ok...  Need a little help. New batteries read 12.5 vlts with the motor off.  With the engine
running the system reads 12.4 volts. I took the alternator in and had it tested.  It tested ok on an automotive testing machine. I do have a dual battery switch.

What could it be???
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Brian
1975 V-173 (The Gravy Boat)
1976 CV-16SS (Greener Grass)
1977 CVX-20 Deluxe (Silver Fox)
1976 V-195
1986 CV-23
1977 T-166XL Sportster (Plan B)
1977 CVX-16

Offline Rich_V174SS

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Re: Charging trouble on a 5.7 alpha 1
« Reply #1 on: July 04, 2012, 07:20:01 AM »
If you checked the running voltage with a digital volt meter and it was not higher than the battery's static voltage then I would suspect the alternator was not charging, or at least not charging with enough amperage to handle both batteries. Do you have a fuse in-line with the alternator output? It would probably be a 90-100 amp that looks like a small red square block mounted on the starter where the alternator output wire connects. Check to see if the fuse is good and also check that all the wire connections are clean and tight.
« Last Edit: July 04, 2012, 07:40:56 AM by Rich_V174SS »
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1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Burnin Daylight

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Re: Charging trouble on a 5.7 alpha 1
« Reply #2 on: July 04, 2012, 07:38:43 AM »
Bryan, when we added the second battery and switch to Burnin Daylight I had a high output alternator built for her.  The experts at the alternator shop said that the stock one that on her would not be adequate to charge both batteries.  I intend to add a second battery and switch to Hot Knots also and expect to have another high output alternator built for her.
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1981 INTIMIDATOR  "BURNIN DAYLIGHT"
1984 CV23  "HOT KNOTS"

Offline ChfBrianB

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Re: Charging trouble on a 5.7 alpha 1
« Reply #3 on: July 04, 2012, 08:23:36 AM »
Were you seeing any charging at all wiyh the stock system? I'm actually losing .5 volts when the engine is running.  I will certainly look into the new alternator though!
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Brian
1975 V-173 (The Gravy Boat)
1976 CV-16SS (Greener Grass)
1977 CVX-20 Deluxe (Silver Fox)
1976 V-195
1986 CV-23
1977 T-166XL Sportster (Plan B)
1977 CVX-16

Offline WetRaider

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Re: Charging trouble on a 5.7 alpha 1
« Reply #4 on: July 04, 2012, 10:46:34 AM »
Not that it had to do with boats ... but when I'd throw mad accessories in a car, it was easy to overdraw what the alternator could provide.  We'd do multiple battery setups, etc.  Eventually, I found a company that built alternators for ambulances ... except for the volvo I'm driving now, I've always swapped my alternator to one of the ambulance versions ...
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If you didn't get wet, you didn't have fun ~ WetRaider

Dan O'Connor
1979 GT 150 / 1976 Mercury 1150

Offline Burnin Daylight

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Re: Charging trouble on a 5.7 alpha 1
« Reply #5 on: July 04, 2012, 01:48:25 PM »
I never ran the stock alternator.  When Red rebuilt her, we went to the alternator shop and were advised to upgrade.  With the 1000 watt amp and all the other accessories that were gonna run in her we knew we needed more amperage. 
« Last Edit: July 04, 2012, 05:22:53 PM by Burnin Daylight »
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1981 INTIMIDATOR  "BURNIN DAYLIGHT"
1984 CV23  "HOT KNOTS"

Offline intimidated

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Re: Charging trouble on a 5.7 alpha 1
« Reply #6 on: July 05, 2012, 11:24:08 AM »
At the risk of asking a dumb question, did you just start the engine and check it at idle speeds?

Single wire alternators need to revv'd up a bit to self excite before they will charge.  mine needs a blip over about 1000 rpm to start charging.
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Offline ChfBrianB

  • Brian Bergstrom
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Re: Charging trouble on a 5.7 alpha 1
« Reply #7 on: July 05, 2012, 02:26:53 PM »
Quote from: intimidated on July 05, 2012, 11:24:08 AM
At the risk of asking a dumb question, did you just start the engine and check it at idle speeds?

Single wire alternators need to revv'd up a bit to self excite before they will charge.  mine needs a blip over about 1000 rpm to start charging.

Yes...  we tried that too.  We ran it up to about 2500 and didn't see any change.
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Brian
1975 V-173 (The Gravy Boat)
1976 CV-16SS (Greener Grass)
1977 CVX-20 Deluxe (Silver Fox)
1976 V-195
1986 CV-23
1977 T-166XL Sportster (Plan B)
1977 CVX-16

Offline intimidated

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Re: Charging trouble on a 5.7 alpha 1
« Reply #8 on: July 05, 2012, 03:01:35 PM »
ya, figured you'd check that.

alt is done.
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Offline Jason

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Re: Charging trouble on a 5.7 alpha 1
« Reply #9 on: July 06, 2012, 12:04:10 PM »
The voltage regulator is built into the alt correct? I think that is how my 140 mercruiser is. I feel your pain Brian as I had charging problems too. Marine alternator's are not cheap and the car ones are so tempting at a fraction of the cost. I ended up finding a used one.
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Jason S.
1974 Glastron Carlson CV16SS 140 I/O
1986 Glastron Carlson CV23 260 I/O
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