Boat Engines and Circuitry?

Question

When plugged in at the dock to a land line charging the boat, I can start the boat quickly and easily, once unplugged if i turn the boat off run off the battery for an hour or two (there are two batteries and i only run off 1 if im drifting or ancored) and i attempt to restart the boat if struggles to start. Can someone help me with what the problem might be?

Answer 1

Check the batterys with a load test as they sound weak> As with the battery charging it give it more power for starting>

Answer 2

A fully charged battery measures at least 12.65 volts.  With the engine running above idle, you should read 14.5 volts.

But even a battery that takes a full charge can still be bad -- most car parts stores will load test a battery for free -- that's the ultimate test of a battery's ability to power a load.

Couple possibilities.

*If one battery is bad it'll drag the other one down.

*You have so many accessories running that there's not enough voltage left for the starter.

Your house battery should be a marine deepcycle battery, and the cranking battery should be a marine cranking battery.  You should have an isolator switch that lets you charge them both when connected to shore power, and lets you charge the house batteries when the engine's running when the cranking battery is fully charged, but keeps them separate otherwise, so the accessories can't affect the cranking battery.  In an emergency you can use either or both to start the engine if needed.

Batteries should be store with a full charge, and topped off every couple months if not used.  Best way to maintain a battery is connected 24/7 to a "smart charger" that switches to "float mode" when it's fully charged.

Add distilled water when the water level drops below the plates.

Answer 3

First check all your cable connections for corrosion and then have your batteries tested if you still have the problem.

If you have a voltmeter your batteries should be at least 14.5 volts when charged up.

Also if you are draining one battery and then using both batteries to start you will only have the same voltage as the lowest battery.