1994 25HP Merc charging questions.

[fatherervin]

Firstly, I love this site. Thank you Iboats!

I just got a 25HP Merc with electric start and manual start. I have it hooked up to an 18' Pontoon and it's a great combination.

My question today is about batteries and charging.
When we got the boat we installed the largest marine battery we could find. So big, it doesn't fit in the battery tray.

We charged the battery up full and went for a few runs.
When I turn on any of the lights I notice a significant drop on the voltmeter. When I turn on the CD player, I see barely any voltage drop.

Does this motor have a charging circut or does it output enough power to keep the running lights going even at idle? (I just put put around with the pontoon)

Can I do any damage to the charging circut (if so equipped) if I continue to run lights until the battery actually dies?

The only lights I have are the two front dock lights (which I only use when I dock or need extra light to see bouys) and the front green/red light and of course the back 36" clear light.

Ideally I would like to be able to run minimally the front red and green lights without worrying about doing any harm to the motor/battery and I dont want it to die on me while out on the lake.

Lastly, how can I measure how much current/voltage draw each light puts on the battery?

I appreciate all comments!
Fe.

 

[rickdb1boat]

Re: 1994 25HP Merc charging questions.

If you have electric start, you no doubt have a charging system. It would be enough to power the lights and other small accessories if working and charge the battery some too. It may not be working properly though. With all accessories off and the engine not running, take a voltage reading at the battery using a voltmeter. Should be at least 12.7 volts. Then run the engine at fast idle(1500 or so RPMs) and take a reading again. Should be over 13 volts and then some. You're really looking for any rise after it's running. If none, there is a problem in the charging system. Most likely a bad rectifier. You should be able to run the boat quite a while on a fully charged battery. Of course, running lights and such will cut down on that time depending on what you are using. You would not want to kill the battery completely. Not good for the battery or other electronics in the engine. It is normal to see a voltage drop when accessories are used, even with a good charging system. Check it out first and let us know....