Re: Battery keeps dieing
I charged the battery w/ jumper cables on my truck at the boat ramp and came home . about a 10 min drive, it was dead when I got home.
I recharged w/ the truck and disconected the running lights and the fuse panel 30 min later still charged trim and tilit working strong. I reconnected the running lights and came back about 15min later still charged so it has to be in the fuse panel. The motor Is a 94 70hp Johnson. Should it charge the battery as I run the boat?
Thanks again
Once the battery is run down, it would take hours to fully charge it using jumper cables connected to your truck. What happened was, right after recharging, the battery has a "surface charge", think of it as some extra voltage, that will dissipate over a few hours (if you were to fully recharge it), or in your case, 10 minutes since you really didn't put much of charge on it at all.
Your outboard shouldn't have any trouble keeping the battery charged if the charging system is working correctly, but once it's run down, you'd have to run it full throttle for a few hours to to get it back up to 100%. If you don't recharge it with a bench charger, it'll go along in a chronic state of undercharge, until it just gets too weak to start the motor.
Adding to the problem, is the fact that batteries self-discharge -- a brand new battery will run down over a few months if you don't recharge it, and it just gets faster as it ages.
If your tachometer stopped working, that's a symptom that your outboard's charging system has stopped charging.
A better way to test the charging system is to get yourself an Autoranging Digital Multimeter (Walmart has one for about $25 -- not the best, but good enough).
Measure the battery voltage with the engine off -- a fully charged battery measures at least 12.65 volts. Then measure it again with the engine running (all accessories off). The reading should be higher with the engine running, and should increase with RPM's (might be little to no change at idle). Any other result, the rectifier is the most likely culprit.
Check the water in the battery, add enough distilled water to cover the plates. Charge it at 10 or 12 amps until done, preferably with a "smart charger" with "float" mode or "maintain" mode. I got one at Sam's for under $45.
Wait 3 or 5 hours for the surface charge to dissipate then check it with your multimeter. Should be 12.65 volts or higher.
If it passes that test, you still should check it with a hydrometer (few bucks at any car parts store), just follow the directions on the package.
If it passes that test, it could still be bad -- only a load test will tell you for sure. Most car parts stores will test it for free.
Storage at less than 100% of full charge is one of the leading causes of premature battery failure, so charge it every couple-three weeks if you don't use it.
