Voltage Problem |
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td_in_nc
Senior Member Joined: March-30-2012 Location: Clayton NC Status: Offline Points: 381 |
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Posted: July-18-2015 at 1:13pm |
I will start this by saying I struggle with solving electrical issues.
I went out yesterday and when I started the boat each time, it sounded like I did not have a lot of power coming from the battery. It would be just enough to turn it over. At one point there was not enough juice to turn it over so I switched to the other battery. It also acted like it was low. When I got home I put the charger on it and it showed both batteries full. I tested with a multimeter and both checked at 12.5+. I cleaned the battery and engine ground connections When I check the voltage at the ignition switch it is it is 12.5, but when I turn to the key to the first position it reads 11.5. I tested the volts from the starter to the ground 12v Tested from positive on battery to engine ground 12v Tested the voltage at the fuse box from Pos to neg and it was 12.5, When I test the voltage from the battery positive to the hot wire on the ignition switch in the on position I get 1 volt (was hoping for 0), if I turn on the bilge I get almost a 2 volt reading.. Not sure where the problem is or how to pinpoint it, but suggestions sure would be appreciated. Tom |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Tom,
One of the things you haven't mentioned is what type of battery(s) are you using. Also, you need to get a voltage reading at the starter when cranking. This will tell a lot since it will show the voltage drop. How are your battery cables? |
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td_in_nc
Senior Member Joined: March-30-2012 Location: Clayton NC Status: Offline Points: 381 |
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I have deep cycle batteries (which what came with the boat with 690 cranking amps an 101 amps/hour
Testing voltage from positive at starter to ground on engine it was 12.5 then when cracking it dropped 11.9 volts. |
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Orlando76
Grand Poobah Joined: May-21-2013 Location: Mount Dora, FL Status: Offline Points: 3108 |
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Oh boy you're gonna get reamed about the deep cycle. That's like asking which tube performs better. I myself feel the stock 351 is fine with it but everybody disagrees. Mainly your batteries won't last long with a deep cycle.
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1976 Ski Nautique 351 Escort 1993 Ski Nautique purple and black 351 HO PCM |
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td_in_nc
Senior Member Joined: March-30-2012 Location: Clayton NC Status: Offline Points: 381 |
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Yep expecting that. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Well, what can I say that isn't already a known problem!!
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Tom,
The .6 voltage drop is not bad at the starter. Considering your batteries are rated in amp hours as well as cranking amps and the low drop, I'd have to say they are combination starting and deep which is a compromise between the two. There's also a chance that the starter isn't pulling the amps, then you will not see a big voltage drop so, I'd look at the starter is self. Personally I'd open it up and check the brushes and the commutator. If the brushes look short replace them and then clean up the commutator. I wish there was an easy way to get amp draw on a starter but it involves a shunt or current doughnut and meter that most don't have. |
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DVskier
Senior Member Joined: September-04-2014 Location: Seneca SC Status: Offline Points: 449 |
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Amprobe.
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21171 |
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Won't take a charge, barely turning the engine over... Time for a new battery. Don't buy a deep cycle. :)
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Find one that will handle 600 amps DC!!! |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Unless stated voltage drop is incorrect, it's saying no but a load test on the batteries is not a bad idea. |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21171 |
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I've been mislead many times by batteries that show "full charge" (12.5v) but don't have the capacity to crank an engine (fast or at all). Load test it by all means, but the fact that they're deep cycle and at least a few years old makes them suspect IMHO.
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baitkiller
Platinum Member Joined: October-11-2011 Location: SW Florida Status: Offline Points: 1693 |
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My guess is a bad Perko switch. I see it all the time and seldom does anybody ever consider it a possibility. I have seen starters and batteries and even cylinder heads pulled for a bad Perko switch, Easy trouble shooting is load test the batteries, Fine? Ok now put the tester on the battery connections at the starter. Low? Put the tester on the switch terminals and you can now load test in and out of the switch.
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Jesus was a bare-footer.............
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Tim, You have been fooled by a surface charge . It will show good volts but you are correct that's not under load. The load test will tell for sure but in this case the starter is close to a load test. With a load tester, it's cranked up to 1/2 the CCA of the battery for 15 seconds and volts shouldn't fall below: Electrolyte Temperature °F Minimum Voltage Under LOAD 100° 9.9 90° 9.8 80° 9.7 70° 9.6 60° ° 9.5 50° 9.4 40° 9.3 30° 9.1 In this case if the readings are correct, the drop was .6 volts when cranking (under load) so that's what's got me thinking starter and it's brushes. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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He's already done that. Please read again. No voltage drop so it's not whatever switch he has for the two batteries. |
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td_in_nc
Senior Member Joined: March-30-2012 Location: Clayton NC Status: Offline Points: 381 |
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Thanks for the suggestions. I will have the batteries load tested,. If they test well I will look at the starter. Will keep you posted but it will be a little while before I have a chance to work on it.
Tom |
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DVskier
Senior Member Joined: September-04-2014 Location: Seneca SC Status: Offline Points: 449 |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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David,
Thanks for the Amprobe info. I'm sure out of date with what's available these days. I should have looked before commenting. I will however forgo the $300 + for now! |
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DVskier
Senior Member Joined: September-04-2014 Location: Seneca SC Status: Offline Points: 449 |
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Good tools = good troubleshooting. I have had an Amprobe since 1985. Many also forego your advice to use a VOM.
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