Boat only starts on shore power

[FireDrill]

Well, this is crazy. When I'm connected to shore power, the boat starts right up. If I disconnect shore power, it won't turn over. Batteries were replaced in April. Yesterday, I took her out for just a short (no wake, 20 minutes) cruise to a marina with a gas pump, and after fueling, the batteries were only registering 10v (takes 12 to start). Got the boat towed back to my marina, connected to shore power, and within 5 minutes she started up.

I was in the cramped engine space yesterday topping off fluids - is it possible I knocked something loose in the charging system? But if the charging system isn't working, why can I start it with shore power? It's very confusing, and I have no idea what might be going on. And, admittedly, I'm still learning about all of this, so I'm sorry if this is something obvious and I'm just not aware of it!

 

[magstang1]

While under way, the alternators charge the batteries. When on shore power your battery charger charges the batteries.

Bad alternator?

Check the battery voltage with everything off and shore power disconnected. You should see 12.5 volts or so. Start the boat and check again. Your voltage should come up to 14.4 or so. If the voltage doesn't increase with the engine running, you have a charging problem.

 

[HUMPH]

Sounds like you need new batteries.

 

[KC_Sundancer]

It's possible one of the new batteries is or went bad and pulling the whole system down when off of shore power.

 

[Mike Blake]

As I always say, It starts with the batteries!!

 

[Saverio]

do you have an emergency start button?

 

[Hifirush]

Mmmmm, when I first got my 330 home, I had a problem with my alternators. The PO replaced the alternator in question, but it stilled did exactly what you are describing. My surveyor caught all this and told me to have the alternator tested, which I did. I found out that my batteries all needed replaced (he also told me they were weak) and that the alternator was indeed bad, even though it was new! I ordered a new alt, bought new batteries and all is well, plus I have a backup alt, I had it rebuilt!

Matt

 

[Bt Doctur]

Start by not using shore power. It has nothing to do with starting a motor . The wrong charger will kill your batteries rather quickly. Basic operation is this: insert key and turn to "on" position. Gauges should come alive and note voltmeter reading. Once motor is started voltmeter reading must rise to atleast 13.6Vor your not charging.
Being a twin, verify that you have true independent electrical systems.

 

[Alegria]

Had a similar situation. Bad alternator. Engine would start with charger on and run. Turn off the charger and the engine would die. Replaces alternator and issue solved.

Sent from my Galaxy S3

 

[GrandMaster]

Well, this is crazy. When I'm connected to shore power, the boat starts right up. If I disconnect shore power, it won't turn over. Batteries were replaced in April. Yesterday, I took her out for just a short (no wake, 20 minutes) cruise to a marina with a gas pump, and after fueling, the batteries were only registering 10v (takes 12 to start). Got the boat towed back to my marina, connected to shore power, and within 5 minutes she started up.

I was in the cramped engine space yesterday topping off fluids - is it possible I knocked something loose in the charging system? But if the charging system isn't working, why can I start it with shore power? It's very confusing, and I have no idea what might be going on. And, admittedly, I'm still learning about all of this, so I'm sorry if this is something obvious and I'm just not aware of it!

Both engines wont start and both port & stbd batteries were only reading 10V?

If the batteries themselves are good sounds like you have an alternator or battery isolator problem.