I made a cursory search among several boat forums about this question but, frankly, I trust our membership more. There has to be a few boat owners here.

I started changing my own oil/filter/gear lube myself a few years ago but haven't replaced my own batteries until now.

My setup is:

- 2 batteries: cranking and deep cycle
- Switch: Off, 1, All, 2
- Standard +/- posts on both batteries

Question:

What order do I disconnect the batteries and reconnect the new batteries to make sure I don't blow them up or cause a spike thru the system?

Battery switch to off.
Remove connections from the (-) terminals.
Remove connections from the (+) terminals.

Replace batteries.

Connect (+) connections.
Connect (-) connections.

With switch in the off position it shouldn't matter. I do hardest to reach to easiest to reach.

But you want to disconnect the Negative first as you can not Arc if there is no ground. I would disconnect Both grounds first. Assuming there is no computer that needs to maintain power.
Wayniac has it

No computer.

There appears to be no ground. Should I add one first?

No, in context ground = (-).

Alright, thank you for the advice.

I'll report back tomorrow so you know the batteries didn't blow up in my face!

I agree with negative terminals first my reference was these batteries are isolated with the switch off and as long as major computers and such are run through breaker doesn't matter which battery first. I get the arcing stuff and surge.

quote:

Originally posted by Wayniac:
Battery switch to off.
Remove connections from the (-) terminals.
Remove connections from the (+) terminals.

Replace batteries.

Connect (+) connections.
Connect (-) connections.

This, but it really doesn't matter if you disconnect the positive or negatives first. But make sure you keep track of every wire that is on the terminal. ALSO make sure you don't his the other terminal with the metal tool you're using to tighten the cable on the other terminal.

It's really pretty easy. I own a Yacht Management business and have been around or working on boats for 35 years......professionally 15 years.

As for disconnecting the negative first and there is no ground.....there are plenty of other places to find a ground if the boat is in the water.....like the bilge water or bonding system for instance.

quote:

Originally posted by jimmy123x:

quote:

Originally posted by Wayniac:
Battery switch to off.
Remove connections from the (-) terminals.
Remove connections from the (+) terminals.

Replace batteries.

Connect (+) connections.
Connect (-) connections.

This, but it really doesn't matter if you disconnect the positive or negatives first. But make sure you keep track of every wire that is on the terminal. ALSO make sure you don't his the other terminal with the metal tool you're using to tighten the cable on the other terminal.

It's really pretty easy. I own a Yacht Management business and have been around or working on boats for 35 years......professionally 15 years.

As for disconnecting the negative first and there is no ground.....there are plenty of other places to find a ground if the boat is in the water.....like the bilge water or bonding system for instance.

Open bow 1995 18.5' Monterey SCR on the trailer in our driveway. Bought it 8 years ago and started maintaining myself 4 years ago. We generally keep it on a slip in Lake Austin but I bring it home for maintenance. Impeller replaced last year.

Any other advice in general?

I think you've got your answer but as an aside I got my battery turned around once just before installation and almost connected to the wrong terminals. Be careful!

Dunno about boats, but on cars you always disconnect the ground first and reconnect it
last. This is because the battery ground is connected to the chassis. If you disconnect the positive first and the wrench touches the chassis sparks can fly. If you disconnect the ground first the only way sparks will fly is if the wrench touches both terminals.

On airplanes I always do it the same way to be on the safe side. Some tube and fabric birds it wouldn't be an issue, but...

If the boat is nothing but fiberglass near the battery it may not matter, but disconnecting the ground first is almost always the safest. I say almost because some really old stuff may have a positive ground...

Next you can change the spark plugs, and any other tune up parts. If the boat is not used for a month or more, it is best to charge the batteries occasionally. Flooded batteries have a self discharge rate of 10% a month, and letting batteries sit discharged is very hard on them.

A solar charger with a proper three step regulator would work well. This should be a two battery regulator.

quote:

Originally posted by c1steve:
Next you can change the spark plugs, and any other tune up parts. If the boat is not used for a month or more, it is best to charge the batteries occasionally. Flooded batteries have a self discharge rate of 10% a month, and letting batteries sit discharged is very hard on them.

A solar charger with a proper three step regulator would work well. This should be a two battery regulator.

What about a trickle charger hooked up to an outlet? My covered slip has one I don't take advantage as of now.

My boat has 3 Group 27s.
I can't remember doing anything special other than making a quick sketch of the cables and wires and where they're connected and to which battery.

It's a bitch, not to mention expensive to replace 3 of these.

I went to Delco brand marine batteries a long time ago and haven't looked back. They're tough.

Ideally, you'd like a 2 bank marine charger. Even though both of your batteries are wet cell, they are different types probably at different states of charge at any given time. A 2 bank charger is effectively 2 chargers, each battery getting optimized individually to prolong life expectancy. The size of the 2 bank should be consistent with your needs, eg. the speed with with you may need a re-charge, typical state of charge when returning to the slip, and the capacity (AH) of the deep cycle. Unless you are digging deep into your deep cycle house bank, you likely don't need high capacity, but with a bow rider, if it's a permanent installation on board, you may want a more marinized charger to handle more exposed conditions. I'm guessing a 6 to 10 amp 2 bank 3 stage smart charger is all you need. Nice to get one with different charge regimens if you move to AGM or Gel later. Expect to pay $80-150 for a decent one.

you may consider a Blue Seas "Add-a-battery" setup

I had a perco 1-2-all switch and had to remember to put in the all position to make sure both batteries charged while underway

since I put the Blue Seas switch in I've had zero problems with keeping both batteries charged, more importantly I no longer have the power drain causing electronics to flash or cut off as each circuit is truly isolated

New batteries in, no injuries.

I did notice minor sparking when I placed the negative jumper on the second battery connecting the negative posts together.

Normal?

generally that means there is an open circuit like lights or ignition on, maybe an accessory switch, or something wired straight to the battery around the fuse block.

quote:

Originally posted by Wino:

quote:

Originally posted by c1steve:
Next you can change the spark plugs, and any other tune up parts. If the boat is not used for a month or more, it is best to charge the batteries occasionally. Flooded batteries have a self discharge rate of 10% a month, and letting batteries sit discharged is very hard on them.

A solar charger with a proper three step regulator would work well. This should be a two battery regulator.

What about a trickle charger hooked up to an outlet? My covered slip has one I don't take advantage as of now.

A lower power "smart" charger would be better. Trickle chargers are 'endless hummers' that do not shut off when the batteries are full. When the boat is being used 2x/month nothing may be needed. However if unused for several months damage is occurring.