Battery question

[Old No 7]

I need to replace my main starting battery but have a few questions before I do. My boat is an 18' CC that is 3 years old, and I have a 90hp 2 stroke mercury motor.

The main battery is used for starting and the bilge pump. The boat is kept in a marina. Most of this season I ended up having to start the motor using battery #2 as (I think) the bilge pump drained #1,

I tend to go out on short runs, 15-30 minutes so there is not alot of time for the motor to charge the battery? Potential problem??

So my first question is should I have the battery switch on both when running or on 1 or 2 seperately. I normally would put it on 1 for the trip out, and 2 for the return. That seemed to work for a while, but then #1 started to fail and would hardly ever start the motor.

My second question is should I get a dual purpose battery for #1? (Starting and bilge pump) We had alot of rain this year so that certainly didn't help, but it seems to me a 3 year old battery should have lasted longer.

last question, can I increase the Max CCA from what I have now if I have the physical room? I'm worried about damaging my alternator. (I'm not sure if the battery has too much capacity it would be overloaded)

Thanks for your help in advance,

Mike

 

[ChampionShip]

Re: Battery question

I would rather have my bilge running off of a battery not responsible for starting my motor. Do you have access to a plug-in at your marina? I would add a 2 bank charger/maintainer to keep them topped off no matter how much rain you get.

 

[NYBo]

Re: Battery question

Perhaps better covers to keep out the rain are in order.

Make sure there isn't a leak that is causing the bilge pump to work overtime. You could arrive at the marina to find your boat resting on the bottom.

No worries about a larger battery damaging your alternator.

 

[Silvertip]

Re: Battery question

Agree that the bilge pump should be on the battery NOT used for starting the engine. As for use of the switch, set the switch to the battery that needs charging the most. That ensures the weaker battery gets the biggest boost from the engine -- over whatever time the engine is running. But even doing that, the short trips do not provide enough charge time. Your engine has about a 16 amp alternator. Not large by any means. You also need a two-bank on-board charger so you can plug in at the dock. Your batteries are headed to "battery heaven" due to lack of charging.