Bad batteries or alternator?

J

justgotaboat

Member
Joined
Jun 18, 2009
RO Number
31427
Messages
159
My friends 24 ft bow rider (not sure exactly what year or anything specific but shouldn't matter for this question)

He got to the marina and both batteries were totally dead. Starter just went “click". Got a jump and the boat started fine. He let it idle at the marina for a bit. Turned it off and back on. Started fine. Idle for a bit longer. Tested again and fine. Went out for a 30 minute cruise and back to the marina. Bathroom break and tested the boat again Incase the batteries failed again. Everything fine. Gauge shows 13.5 volts or so when engine is running. Goes out again and stops at friends house for 45 minutes. Batteries are too weak to start the boat. Engine turns over barely but can't start. Jump again and runs fine.

I say it's bad batteries. He is questioning if it's an alternator or something else. He has never changed the batteries and owned the boat for 6-7 years.... so assume batteries are at least 7+ years old. He doesn't think he left anything on since he used it last. And he knows he didn't leave anything on throughout the day.

Opinions?

Thanks!!
 
He got his money's worth out of those batteries. Time to replace.
 
Should be getting 14.4vdc especially with the alternator turning above idle. You can confirm
with a load tester - but it’s the batteries. 6-7 years from SLA batteries, they owe him nothing anymore. And if they’re AGM’s, they turned into junk with special ha sling requirements the moment they completely discharged.
 
Batteries. The alternator is working. If the batteries are flooded wet cell type with fill caps, has the electrolyte level been maintained to at least cover the tops of the plates?

Suggest he put at least the one with highest disconnected-from-boat voltage on a good 10-20 amp multi-stage automatic charger to see if `it can eventually reach 100% over many hours. (A good charger will tell you if it is unable to attain 100% or if the battery is clearly "bad". Some will also automatically enter a "desulfation mode" if the charger senses that may be needed to help clear buildup off plates. That may or may not make any difference.)
Then apply a slight brief load to remove the deceptive float charge, and test ( free at a battery store) with a conductance analyzer & resistance load tester.

That said, it's best to replace both batteries at the same time so the boat charging system is sensing batteries in the same condition/ capacity. 6-7 years use is very good longevity for marine batteries. RIP.
 
We put one on a charger and it never reached full capacity and the charger indicator never said it was fully charged after 8+ hours of charging. Put the second on the charger and it read full charge almost immediately, but pulled it off the charger and immediately the volts would drop when checked with a voltmeter.

Put two new ones in... and hopefully that will solve the issue!
 
Replace the batteries I have never gotten 7 years on a battery ever!
 
Agreed with replace batteries first. I put batteries on a charger and if they take forever to take a full charge, then you know they shot. They really should be load tested as well. My charging voltage with a new alternator is 14.2V. I would also check all battery cables and terminals for corrosion. Also make sure that the battery connection on the starter solenoid is clean and free of corrosion and don't forget the ground terminal on the engine bell housing. If the battery terminals at the battery use wing nuts get rid of them. They get loose and cause all kinds of problems. I used marine grade automotive style clamps bolted on the terminal end on the cable, that way if they get corroded I can easily replace them. If he keeps having this problem its a good idea to check for amp draw with the engine off. I had a similar problem and found my GPS was re-starting itself with the engine off. I connected an ammeter in series with the neg battery cable and found it that way.
 
quote:
Originally posted by Audrey II

Replace the batteries I have never gotten 7 years on a battery ever!

Click to expand...


Date label on mine is 11/2005 - but I take good care of my boat and camper (2011) batteries.
 
6-7 years on a battery is WAAAAAY to long. I change batteries about every 3 years. Hate ruining a day on the water due to bad batteries.
 
I ve never gotten more than 5 years out of batteries even AGMs

If voltage goes up with engine running (13.5 to 14v or more) then the alternator is charging. Lilly the batteries unless he has a big load on
 
Come on Penney pincher; break down & put new batts on board! Had many years of 6-7 years but why push it? Not worth it!
BOB J
 
You must log in or register to reply here.
Back
Top