Pontoon Boat & Deck Boat Forum

I need some of you electrical wizards out there to put on your thinking cap. We went out yesterday and I started on both batteries. It had been a few weeks since we were out and I thought I might charge both a bit.

I forgot I was on both when we toured the lake and pulled the girls on the Big Mable. We were heading to a sand bar about 10-15 MPH (3000RPM) when I noticed the voltage falling. It got down below 12 and when I tweaked the trim, it dropped to below 10. At this point I switched it to Batt 1 but it still stayed below 12. I thought our day was over.

The motor would not start on Batt 1 but would with some sluggishness on Batt 2. We decided to head to the marina. After a period with all loads off (stereo), the charging voltage came back to just under 14. I switched to Batt 1 and charging continued to look good.

I ran around the lake near our marina and after a bit, both batteries would start the motor. We continued our day running stereo on Batt 1 and leaving Batt 2 to start only in an emergency.

Left it on Batt 1 rest of night while moored, playing stereo and watching fireworks till after 10pm. Motor cranked okay on Batt 1 and we motored on home.

Anybody have any thoughts on this issue? The charging system is rated 44 amps on our motor and I'm not real confident that it could be an intermittent problem.

Sounds like the charging system was overloaded and not charging. Or maybe a connection or poor switch contact, maybe. Those are the things that will drive you nuts.

I'd check the battery terminals and anything else you can get to. You could start the motor and check the output voltage with a multi-meter (not that you voltage gauge is wrong) just that you can check it in multiple places to see if you can find a poor connection.

Since you say the voltage returned to normal I'd suggest not only looking for a loose connection but actually taking your battery connections apart cleaning them with a wire brush till bright and shiny then apply dielectric grease to improve the bond. Corrosion even when you can't see it can do funny things...

Check connections including both ends of the ground.

You'd be surprised how often that can cause issues.