Battery acts like it was dead

[kbur]

Took the boat out today. When I first got into the water ready to take it off the trailer, I had to jump it. I let it run for a bit and when I went to Trim down it instantly killed the motor. It happened twice, pulled out and out of the water I could trim up and down no problem with the motor off. I went back down to put in the water, had to jump it again, boat didn’t die when I trimmed down. I did have to jump after shutting it off every time. Nothing running in the background while off; radio, blower, lights, etc. got the battery tested and the battery is not at fault. 4.3 mercruiser

 

[dubs283]

got the battery tested and the battery is not at fault.

If the battery was load tested proper and is the correct rating I'd be suspect of the battery/starter connections including grounds

If all are clean and tight a voltage drop test can help pin point the issue

 

[kbur]

Boats out of the water. Can’t even get it to turn over now.

 

[Bondo]

Boats out of the water. Can’t even get it to turn over now.

Ayuh,..... Welcome Aboard,..... Load test the battery,....
While yer at it, remove, 'n clean to shiny metal both ends of both battery cables,.....

 

[dubs283]

Can’t even get it to turn over now.

Ya dude, 99% chance your battery is dead an incapable of returning to a useful life

Fairly common with boats, battery condition is near, if not #1 priority

Your next battery(s) needs to be the correct rating for your setup of a quality brand. No cheating out with fundamental power systems

 

[Scott Danforth]

Either really bad connections or a bad battery