Oddball Starting Problem

[Monte Cresto]

I went to the boat today to start my Yanmar 3JH2E in my DownEast 32 and
experienced these starting symptoms:
Battery bank on "All" with +12V across the Bank.
Turned the key and heard a fast start solenoid sound after that no clicking.
I measured a current that fluctuates between +6 and 10V (battery cables connected) over the entire bank of 4 batteries.
I plugged in a trickle charger and measured a charge complete of +12V again.
Unplugging the trickle charger I again measured a charge of +6 to 10V.
The instrument panel warning buzzer and lights seem to work ok.
I have a gut feeling that it could be the Master Battery Selector Switch, although, it looks and feels ok when selecting bank 1 or 2 or both.
I'm 73 and find it a little difficult crawling around the tight engine compartment so thought I'd run it past the Forum before returning to test the solenoid, starter etc.
What is your idea of the problem cause? Thank you!

[meridian28]

6~10 volts is a dead battery.

[Monte Cresto]

I forgot to add that after removing battery cables I measured
+12V again across the bank, so all batteries are up to charge.
Thanks

[sailorchic34]

A fully charged 12 volt battery or two 6 volt batteries in series will read at least 12.7 volts. If all you have is 12 or 12.1 volts then the voltage slump when cranking could easily be below 10v.

A trickle charger which is Generally a 2 to 6 amp charger, would take something north of 12 to 48 hours, or longer, depending on the size of the bank.

A old battery can show a full charge but will be unable provide High amperage draw. That is how batteries age.

I see new batteries in your future

[Monte Cresto]

Thank you for your reply...I measured the bank just before leaving
and The DVM voltage was 12.87 volts with all 4 12V batteries.
However, you could be right! TKS

[sailorchic34]

one thing to check before buying new batteries , is to make sure all the connections are clean from the batteries to the starter. it can also be carboned arced contacts in the solenoid.

If you're industrious you can take the solenoid apart clean and rotate the contacts and that will fix it for quite a while if it's bad solenoid.

Though as the voltage drops it's probably not the solenoid. Corroded wiring connections could do it.

Edit, I have seen battery cable and damp locations nearly corroded in two.