Bad alternator?

[JohnO]

Took the boat out on 6/7 for the first trip of the year. Two fully charged batteries with a VSR between them. (6th year with this set up. never any problems)

The only time the motor had been run since charging the batteries at home was when I put it in about a week earlier. (Total time about 10 minutes)

Boat started right up. Motored out to the cove, anchored and sat for a few hours. Didn't even play the radio for most of it. Came back to the boat after about 3 hours of kayaking and when it was time to go, turned the key and had nothing. No movement at all on my voltage meter.

Great. What could this be. So I'm thinking that I'm now stuck out here when I remembered my two freshly chraged trolling motor batteries (Yep I've got 4 batteries on board)

So I took out the two starting batteries and swapped in one trolling motor battery.

Boat started right up and ran beautifully all the way to the dock. Tied off to the pier and turned off the motor. Went to raise the motor and had nothing! Again, nothing on my meter. I'd managed to somehow drain three batteries in one trip.

Took the two starter batteries home to charge and they were both around 40% (at about 12 volts when they are normally 13.2 V) They charged right up and held the charge


I've got a 2006 Yamaha VMAX 175HP HPDI motor. Have had no problems with it whatsoever. Have never moved the battery switch while the motor was running. Always turn everything off when I leave the boat. (in fact when I leave for the day I physically disconnect the batteries. I'm kind of OCD about it)

Does this sound reasonable? Are there other things I should look at? Any guesses as to how much this will cost to fix (parts. I know labor will be painful as I'll have the marina fix it as I'm mechanically inept)?

[HandymanHerb]

shouldn't have ran down that quick, I think I have the batteries checked first, with two batteries your should have been able to run for days before they ran down, I betting you have a shorted cell on a battery

[JohnO]

I'll have them tested just in case, but what are the odds of having two entirely separate batteries (the two starters in parrallel, and the Trolling) have the same failure?

[HandymanHerb]

Well if you ran down the TM battery then you have a short in the wiring to look for, to run down three batteries it shouldn't be hard to find, you have a dead short some where draining the batteries

[Bamby]

No movement at all on my voltage meter.

What did the meter read when you got it running? As far as a dead short goes, I'm thinking it's doubtful. A dead short of this caliber would melt down the wiring harness back to the battery provided the wire wasn't fuse protected as it should be. I'd first verify that the batteries are good. I'd then pop the cover off the motor and check that both the ground and hot are tight, clean, and securely attached to their perspective mounting points. If they appear ok I'd then follow the line-set back to the battery(s) checking any obvious damage. But anyway I'm thinking you've got something loose or interment creating the problem.

[babock]

By the way, a fully charged battery is 12.6V. Measure a battery around 30 minutes after you pull it off a charger so that the surface charge has time to dissipate.

[tommyz]

Get a digital multimeter, then check your current draw through each battery feed. That will tell you if you have unwanted draw from somewhere, or just bad batteries.

Pick a charged battery, then disconnect everything from it, then connect the engine only. Key off should be no current draw. Anything more is a problem.

Then repeat with the other feeds to console, etc. With everything switched off you should have no current draw.

If you find something drawing current even though it looks to be off, then that thing is your problem.

Given your symptoms though, it would have to be a fairly high draw to drain a battery that fast.