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battery draining 1989 5.8

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dtwolcot2

Member
Im working on a OMC 5.8 for a friends dad and I believe it is a 89' or 90'. Now when the boat sits in the yard for a couple of days the battery is draining. It just started and the only thing that has changed is that I installed a cd player in the boat for him. I hooked it up the same way as mine boat with a constant battery feed to keep all preset and stuff stored. My boat has sit for 3-4 weeks before and my cd player has never drained the battery. The cd player seems like the obvious because thats the only thing that changed but I cant see that it would drain the battery that fast. I believe the owner did burn up the alternator at the lake last time because I only get 12.3 volts at idle and muster a lousy 13.2 at 2500 rpms on 2 different batteries that are charged. When he asked me to look at it the neg battery terminal had barely been connected. the wing nut was only on a few turns and complained that everything in the boat would loose power for about 30-45 sec, but the engine would stay running. Could the alternator be draining the battery when not running? I am charging the battery now and disconnected the cd player and going to get the alternator tested tomorrow.
 
Re: battery draining

An alt can drain a battery if it has a problem since it has a direct feed from the battery. Could be the regulator is going or gone, voltage seems low. Why not take it in for a bench test?
 
Re: battery draining

sounds to like the reg is going if the points stick on the inside it will drain your battery a quick way to test your chargeing system with the ignition system off pull your neg cable if you see are here spark most cases its the regulator, anytime a wire are cable is shorted on a ford system the regulator useally blows, now if you dont here are see a spark then it useally the alternator are a shorted wire, the only reason i say this is im a ford man ive wired fords and boats with ford engines in them, heck all my rideing lawn mowers are wired ford style they are the easiest to trouble shoot
 
Re: battery draining

If I recall when I changed the batteries it didn't spark. As. Stated before I am taking the alternator in tomorrow for a test and I did dsconnect the radio to check it in a couple days to see if t would drain the battery. The radio works fine and I don't see how it would drain a battery in 3-4 days unless its left on, and the face is disconnected
 
Re: battery draining

the way to check for a parasitic draw, is to remove the positive batt terminal and put a multimeter on AMPS (good quality meter with a fused 10A scale) in series to re bridge the connection. Leave everything switched off.
The ammeter will show how many amps of parasitic current there are.

Then, watch the meter while someone removes each fuse, one at a time.

When you see the amps drop off, bingo.... that's the faulty circuit.
 
Re: battery draining

Took the alternator in today and it tested good. As for checking the parasitic draw I tried that and maybe hooked it up wrong. I had it set to amps and I put one lead on one end of the cable and the other lead on the other and I didn't get a readng. Could you explain more on hooking it up. Not real sure how to hook it n series. Thanks
 
Re: battery draining

dtwolcot2 said:
Took the alternator in today and it tested good. As for checking the parasitic draw I tried that and maybe hooked it up wrong. I had it set to amps and I put one lead on one end of the cable and the other lead on the other and I didn't get a readng. Could you explain more on hooking it up. Not real sure how to hook it n series. Thanks
Click to expand...

One lead goes on the postive (red) cable that you remove first and then the other lead attaches to the positive post on the battery, good news about the alternator although it did sound like a toasted regulator.
 
Re: battery draining

I did the parastic draw test as you said. Without the cd player hooked up it is not drawing any power so that's good. With the radio hooked up it the meter read -0.62 to keep the memery stored in the radio. Is this drawing enough power to drain the battery in 3-4 days? I charged one battery with a slow charger all weekend and now got the voltage up to 13.1 from just the battery and the other battery must be shot now because I hooked it up to the charger and the trouble light comes on. I guess with the battery fully charged and there is no draw on the battery without the radio I'm going to hook the radio back up to see if that much draw will drain the battery that fast.
 
Re: battery draining

I'm sorry I failed to mention that with the fully charged battery and the engine running at idle the the voltage measured 13.9-14.0 and at 2500 rpm it measured 14.25. The battery is fully charged and the alt tested good. Shouldn't I get 14.2 at idle. I'm also going to check the draw on my boat with the radio and compare results
 
Re: battery draining

dtwolcot2 said:
I'm sorry I failed to mention that with the fully charged battery and the engine running at idle the the voltage measured 13.9-14.0 and at 2500 rpm it measured 14.25. The battery is fully charged and the alt tested good. Shouldn't I get 14.2 at idle. I'm also going to check the draw on my boat with the radio and compare results
Click to expand...

Not necessarily, although today's alternators are much more efficient than the old generators you will find the output does pick up some as the RPM's increase so yours sounds good.
 
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