After two summers and a winter of virtually no use I go down to the boat (Hunter 27) to check on things and one of the batteries is showing no voltage on the built in meter right by the battery switch. So I replace it with another deep cycle marine battery and lo and behold both batteries show normal charge now.

So I start the Yanmar diesel engine before I leave to make sure everythings ok and it starts and runs fine but a red light on the control panel next to where you insert the key stays on the whole time the engine is running...about 5 mins. It says 'CHARGE.' I'm assuming this means the batteries aren't charging possibly?

Can anybody tell me what this means and what I need to do to fix this fast?

I wonder if somehow this 'no charge' condition is what lead to the one battery showing no charge on the voltage meter. Possibility?, but I would guess the other battery would have shown no charge as well. I dunno.

Second question is...does my diesel Yanmar engine use any charge from the batteries when it's running? As far as the engine is concerned, is the only time it uses the batteries is when it's starting? If I recall correctly diesel combusts in the cylinder just by compressing it. If this is the case, since my 2 deep cycle marine batteries can crank the engine for a really long time, I could reasonably expect to take a day trip out say if I only needed to start the engine probably twice, even if the charging system was somehow faulty.

To be honest, I'm willing to risk it a little because, well, I got a hot date planned!

I took pictures of the before wiring and checked 3 times after I got the new battery in, so I'm almost positive the wiring was reconstructed correctly.

Thanks for your help.