So a couple weeks back I had a problem with my boat running over the battery threshold 17.6 or so. This was not normal so I went to a supra dealer and they had an alternator. I replaced it on site and cranked her up. She started and seemed to run fine. The volt meter showed both batteries around 14.0 at idle. I did not get a chance to go out on the water until yesterday (3 weeks later) . I started her once a week just to keep her running. I kept my eye on the volts via dash board and they showed around 14.0-14.3.
9/6/2014 (Saturday)
When I got out on the water as I was leaving the boat ramp just coasting in the no wake zone, the boat still read 14.0 volts. As soon as I got to the spot I was going to ski at I saw a threshold warning and saw the volts were at 11.5. I road for a little while and the voltage slowly started to creep down so I came back in. Made it back and the boat said 10.9 at this point! Something is not right.
9/7/2014 (Sunday)
I took both batteries out of the boat and charged them over night. Brought both batteries to advanced auto parts to get them to test them out. One was good and one was bad. So I replaced one of them and installed them back in the boat. I started the boat back up and the dash read 11.6 volts and the Threshold warning was back!!
I turned the boat off and charged the older battery of the two for a couple hours and checked both of them with a volt meter after. Both read about 13.0. I started the boat up and they both read 12.67-12.7 at idle. I had someone get the RPM's up as I watched the volts on both batteries and they did not rise. they actually dropped some not much but some. While I watched the volts with the volt meter the dash read 11.7 which was off some. When I turned the boat off I checked the batteries again and they read 12.67.
So now I am trying to figure out my next step. I replaced the alternator and both batteries. But it seems like the alternator is bad. Maybe it was a rebuilt one or maybe something else. Any suggestions anyone? The alternator cost 300.00 so I would expect it to work perfectly!
Thank you for the responses in advance!