Battery killer?

3 yr old battery wouldn't turn the engine. New battery did once, then went completely dead. What's up? I hope it was a bad battery......

Start with sanding all of your connections and then tighten everything back up wrench tight. It's not always the issue but vast majority of the time I see a battery suddenly go dead, it's a corrosion issue.

Possibly a bad starter solenoid or switch. What Dante said is a good start. Pull all your connections off and clean the lug as well as the surface that it is connected to. Get a stiff wire brush and a battery post brush to do this.

When you go to start it and it doesn't start is their any sound? Do you here a fairly loud clicking back by the engine? If it is clicking then the solenoid should be ok. Also a good idea would be to get a multimeter and check actual voltages. If you can get the boat started check the voltage at the alternator. Make a note of the voltage. Then check it at the batteries. If there is a difference of .2 volts or more that is significant and your batteries aren't receiving the full voltage they should. If it is low then I would check voltage at the starter and see if the problem is between the alternator and starter or the starter and batteries.

Here is another question. when you put in the new battery did you start the boat and immediately turn it off or did you start it and run around for a while? If you ran around for a while and the battery did get and charge it may be a bad alternator. If you started and just turned it off maybe the battery you bought wasn't charged all the way first.

Clean the battery connections on the sterter too.

Assuming all your connections are clean & getting good voltages, you can pull the starter & the alternator & have them tested. A descent shop can do it in the boat too.... but you have to be able to run the boat. It's possible the starter is requiring too many amps to turn over...... maybe it's been wet or is getting older?

Thanks guys!

After putting the new battery in it started, but seemed weaker than normal. After running it for about 5 min I turned it off, so that may have been the problem, but after that it wasn't even a click or anything from the battery. I will clean up the connetions and the starter as well. Thanks again!

Thanks again! Cleaned up the terminals and connections, put some terminal wax/lube on and it started right up. Appreciate it.

Tech tip: very hot water is excellent at cleaning battery terminals. Put water in a cup, microwave it, and dip the terminals in the cup of hot water.
Then cover it with terminal grease of course.