New battery and boat still dies

[Courtney C 0]

I have a 1991 ski centurion. I bought a new battery and had the alternator tested Reads good. Boat started at home and went to the lake went out on about a 10 minute ride and boat dies go to start and doesn’t start like a died battery. Go charge battery get the boat started and take it out again and dies again and won’t start. Any clues?

[Wylie_Tunes 146]

Need to test the alternator output while on the boat, all hooked up like normal. 

[Courtney C 0]

How do you do that?

[Wylie_Tunes 146]

Digital volt meter across the battery posts with engine running. Meter shows what the battery is getting. 

[Courtney C 0]

Okay thank you I will try that 

[rhino89523 34]

Most boats will run once started even with a dead battery if the charging system is working properly. I know you had your alternator checked but it seems like one of your wires isn't hooked up right or corroded. I don't know what alternator you have. If you have a one wire I would be looking at the one wire both ends and connections. If it is not the internally regulated style and you have a voltage regulator I would check all the connections to that and the regulator itself plus the charging wire back to the battery.