Hooked up batteries incorrectly... How much damage did I do?
 

I have a dual batter setup in my supra with them connected in parallel to a perko dual battery switch and had to replace a battery. I accidentally hooked up the two batteries in series and doubled the voltage to 24. I even started and ran the boat for a couple hours before I caught my mistake. I rewired it and it is correct now, but I am not sure if I messed anything up or not by running at double the voltage. There was a bit of a whine coming from the engine bay and the engine temp ran a bit high but other than that, I did not notice anything when running at 24 volts. Can anyone think of anything that would have been ruined from my mistake?

I think if anything was ruined you would know it now.

I would say you need to go out and run it and see what you have going on. I worked for Caterpillar for 7 years and there are common components between the 12 and 24 volt systems. But computers, ecms, starters, electronic gauges, and the like are 12 volt or 24v. So those are the things I would be worried about. Surprised you didn't get some kind of warnings.

You don't say how old the boat is either. The newer the more computer stuff and they greater potential for damage. If it's an older boat that is still mostly mechanical you might be ok.

Its a 2006 Supra 24ssv, so it probably has plenty that could have been damaged. I dont have time to do and run it today but hopefully I can tomorrow. I am surprised too that I got no warning lights or anything. Looking back, I probably should have noticed how fast it cranked when I started it but I just thought it was from a new battery. sure makes me feel like an idiot though...

I agree, run it. If it was gonna let the smoke out, it would have probably done it b now. Operate every single electrical thing on the boat, including taking a digital volt meter to the battery and measure the alternator's output directly.

The 14 volt alternator will not be able to maintain the original 24 (or 25.4) volts. So during the course of the several hours of operation the battery voltage would steadily drop and eventually fall to 7 volts per seriesed battery if given enough time. What the original voltage was, for how long and what the voltage settled to, who knows. Here's hoping you got lucky.

David
Earmark Marine

guessing you might see issues later with bulbs, stereo equipment, and your charging system. Your generator would have been working at 100% duty to try and charge a big 24v battery. Things like light bulbs would (if unregulated) would run brighter and hotter, decreasing their life. Stereo equipment or other electronics might have been running hot too.

I have to think that the motor started right up :)

I also kinda in the camp that you lucked out.

Also how old and in what shape is the battery in the boat that you did not replace? If it was old and tired, it could have been around 9v and lowering your overall voltage when in series

The other battery is around 3-4 years old I believe but is in pretty good shape. But the engine started in a heartbeat at 24v... this should have been a warning sign looking back but I just attributed it to a new battery... doh!
Luckily, I happened to not use the stereo, any lights other than gauge lights or much else when I used the boat yesterday. Hopefully tomorrow I dont get bad news.

Thanks for the help.

if it is all working than it is fine
nothing that you done can raise engine temp, something else or you are just looking to hard

Bulbs burn out fast. You need to pay attention to your alternator charging as a diode could have been damaged, but probably not.

Well I just finished checking everything, and EVERYTHING works... Somehow I dodged a major bullet on this one. The stereo works fully, perfect pass is fine, and all lights are still working. The older battery was running at about 10v while the newer one was at 12v. Maybe the older battery running at just a bit low helped just a bit?

Now I just have to hope that I didnt cause anything to wear out sooner...

I'd say thats Merry Christmas to you!!!

Your battery showing 10V is dead. If its 3+ years, old, replace it come spring or now if you are still riding.