battery charging problem

[gparadise]

I recently acquired a 14ft boat with a 1970 Evinrude 40 hp lark (40073A is the model number). The motor fires right up. I don't think the magneto will fully charge the battery so about halfway through the seaon I'll have to charge the battery. I want to put a marine radio with 4-5.25" speakers, a 12volt cigarette lighter, and possibly a navigation. I'm thinking a standalone battery to run these things but my question is, how would I keep it charged? Or would you suggest doing something else to run these devices?

 

[LippCJ7]

Re: battery charging problem

Your motor is going to have issues charging that setup(with stereo) all by itself, your probably going to need to charge the battery each night before you use it in order to keep it from going dead, a better solution would be to have two batteries, one for the stereo and on for the motor, charging them both the night before you go out, this setup will eliminate the possibility of leaving you stranded.

You simply don't have enough charging power to run a motor and a stereo without jeopardizing the ability to get home without another battery.

 

[NYBo]

Re: battery charging problem

Welcome to iboats!:welcome:

I don't think the magneto will fully charge the battery so about halfway through the seaon I'll have to charge the battery.

What leads you to this conclusion? What is the amperage output from the outboard?

 

[gparadise]

Re: battery charging problem

Thanks guys. I'm new to this boating thing. I was told that as long as my magneto has a rectifier that I should be ok with that set up on the single battery with it running, I would just have to charge it when I get back. Does that mean if I stop and drop anchor with the radio and stuff on that I have to leave the motor running? And how would I know if the magneto has a rectifier? I'm not sure what the amperage output from the outboard is...its a 1970 evinrude 40 hp lark model #40073A if that helps any

 

[UncleWillie]

Re: battery charging problem

Place a voltmeter on the battery, notice that it read ~12.6 volts.
Now start the engine.
If the Battery Voltage goes UP and eventually is in the 14 volt range, The Battery is being charged by the motor.
If the motor has electric start it will almost certainly have the capability to recharge the battery.

You can stop and run a radio and a fish finder for a while and still be able to restart the engine.
Keep a Meter handy. If it gets below ~12.2v, that is long enough!

You will need to experiment at first.
You may be able to run the radio for an hour, or 10 hours, depending on the radio and the battery.