View Full Version : strange electrical power drain

04-09-2017, 04:48 AM
OK towards the end of last season I noticed a strange power drain on the electrical system. It started out one day out in the lake with the engine off and the radio on(not a huge system just the radio and the speakers, no amps or other), after only about 5 minutes the starter had a hard time turning over, it did fire up and I got back just fine. Anyway I thought there might be a short or something in the radio setup so i went on diagnosing it, I did not find anything there. I then checked the alternator and it tested out fine as well. Then a while later we were out at night again engine off but this time no radio just the lights and the exact same thing happens. Now the strange thing is if it sits normally without any accessories on it fires up like normal but any little thing on seems to be a huge drain on the battery. I even thought it might be my battery and swapped it out with another I had to no luck.

any ideas?

forgot to add this is on a 93 prostar 190

04-09-2017, 08:30 AM
Interesting issue. Try taking voltage drop measurements across each battery cable segment, both positive and negative while cranking engine (don't allow to start). If less than half volt drop while cranking is observed on all segments, you can rule out your starting circuit. If more than half volt drop...start inspecting for loose or corrosion in copper strands, terminals, connections, etc...

04-09-2017, 08:37 AM
Forgot to add in previous post:



04-09-2017, 10:10 AM
most likely the alternator - rectifier probably draining battery - had that problem when I first got the boat.

04-09-2017, 12:42 PM
I then checked the alternator and it tested out fine as well.

Define fine?

Battery's at rest static voltage level?

If nothing is turned by you and it seems to start fine, seems to indicate no parasitic drains. Audio or lights on for awhile and its hard to start, sounds like a weak alternator or failing battery.