Drained batteries, vapor lock, or?? (Slow start)

[Chatty21VLX]

2001 vlx with 320 Monsoon... I have had the boat a year, and it has been very reliable. It has always cranked on the first turn of the key. Yesterday, we were out for about 4 hours, and alternated between floating, cruising, and wakeboarding. During times of floating, we would sit for an hour with the stereo as the only battery load, although perko switch was still in the All position (stereo is directly wired to one battery, so switch position shouldn't matter if house loads are off). At one point, I did practice filling and emptying a new ballast bag with a 5 amp overboard pump, and the engine was off for this. After the ballast bag emptied, the motor started just fine and we cruised 10 mins or so at 25mph to a new spot. I put down an anchor and boarded my friend's 23lsv to surf for about 15 minutes. Got back on my boat and turned on the cabin lights and tower lights (six 55 watt halogens) because it was getting dark. Floated for another 5 minutes before it was time to head back. Hit the key, and it just turned over like the kill switch was removed. I checked it, and everything was in place. Tried again 3 more times with same result (turned key 3-5 seconds each try). I turned off all lights, stereo, and even the blower to try again. It very reluctantly started. PP gauge read 11.7 volts after it started. Battery voltage read 11.9 on the very short trip back to the ramp. When I hit the no wake zone, it dropped to as low as 11.4 volts. 

Sorry for the long post, but I wanted to include as much info as possible. Does it sound like weak batteries (I fully charged them the night before our outing), vapor lock, or something else? I plan to go out tomorrow, and have charged both batts again today. I just don'twant to get stranded, especially with guests on board!

[minnmarker]

Six 55 watt lights at 12 bolts is about 30 amps of drain. You drained your batteries. With that kind of load you need bigger batteries and an ACR to keep the starting battery fresh.

[henrik]

Pretty sure I have the same lights on my boat. If I hit the switch the voltage drops immediately to around 11 Volts. Hope to replace them with LED's some day. 

[MalibuNation]

When you cranked it the four times times did it sound/turn over normally/strong?

[Chatty21VLX]

2 hours ago, MalibuNation said:

When you cranked it the four times times did it sound/turn over normally/strong?

Yes, at first, but got weaker for the last second I was holding the key.