Battery problem

First off, I have a 17 ft key west with a 90 hp yamaha on it. The boat is a 1990, but the motor was put on in 2003. I have an Optima Blue top that is probably about 3-4 years old. I will look when I get home but recently I have been having a problem keeping it charged. I first had this problem b/c I hooked everything directly to my battery,(motor, bildge, fish finder, and 4 speaker+head unit sterio). And as anyone would expect. The battery ran dead between uses (sometimes a couple weeks). Then I installed a battery switch with only the bildge drawing constant power. But it may be the battery getting old or wiring problem/ corosion from salt. But recently I went to take it out a couple days after it had been run and the battery bearly trimed the motor up and down and it wouldnt turn over. I then put the charger on it with the battery switch off and got pretty close to a full charge, or so the meter on the charger looked. with the charger still connected i turned the switch on and the charger went right to full charge. Then i turned the switch off and it went back to charging. Why is this? I have always wondered if my outboard has a alternator on it to charge the battery when running. I assume it would be small if it even did. But I am going to take a look when I get home about the wiring and go get the battery tested also. But My worry is getting out fishing while anchored with the motor off and the fish finder on and sterio going, and my battery dieing. When I was out last after my charging as I mentioned earlier, it started but wasnt a powerful start. I felt the battery wasnt charged when the charger said it was.


sorry for the long confusing post. any susgestions. I dont know how long those optima's are suppose to last but for what I spent on it. I thought it would last longer.


Will Vallotton

Re: Battery problem

Your 90hp Yamaha should be able to keep your starting battery fully charged. It sunds as though you may have quite a bit of stuff hooked up to it and may want to consider a separate deep cycle battery for the other stuff that you will need to keep charged with a battery charger as the outboard would need to be run for hours to fully charge a deep cycle.
I recently installed an onboard 3 bank charger for my boat and I'm sorry I didn't do it sooner. I get home and plug in the charger and walk away. All 3 batteries (2 starting and 1 deep cycle) are fully charged and ready to go when I am.

Re: Battery problem

If you run all of those accessories for several hours, run back to the dock in 10 minutes, the battery will go flat since it takes a very long, wide open throttle run to charge a deeply discharged battery. Batteries that are left partially discharged will die quickly. As suggested, have the battery load tested. If it's ok, then start the engine and check the voltage at the battery (or on your dash mounted voltmeter) for 13 - 14 volts at about 1500 RPM. If it does not reach that level you have a charging system problem. If that checks out, then install an onboard charger. Plug it in at the dock and leave it.

Re: Battery problem

I totally agree with the aforementioned advice, if you're dragging that start battery down low often you need a deep cycle because you're likely to kill the battery. But don't depend on your outboard to keep the deep cycle up you will likely need to install an onboard charger or at least charge the battery when you get back with a portable. Deep cycles don't mind being drained and recharged but they aren't the best choice for starting imo. If you go with a deep cycle for your electronics and a cranking battery for your engine you'll always have plenty of power and a back up in case you end up with a dead cranking battery one morning.

A 1/2/off/both switch will allow you to keep your boat wired pretty much as is, instead of everything going to the battery post on your existing battery it would go to the common post on the switch, then connect your starting battery to position #1, and deep cycle to position #2.

crank the battery in position #1, drive out to wherever you're going to be sitting and switch over to #2.

Re: Battery problem

I had the battery tested and the results said that the battery was bad. It was an optima blue top that was purchased in 2003. I figured I got good use out of it. I kept it and will use it to power my jon boat on a small pond. But how long should I expect a battery like that to last. I figured 5 years with little attention to maintenance was alright. I got a new deep cycle battery and installed it and everything works good. I am going to see how the same set up with this new battery works for a while because I had no problem for the past 5 years until now. so i figured I will try it for a while until something changes.