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How to check Alternator??


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I did a search and did not come up with much.

I put a new marine battery from NAPA this spring due to my old one being dead. NAPA replaced the old one at no charge due to it being dead and only a year old.

So off to the lake last Wednesday boat runs great played the stereo awhile and went home.

Saturday went to start the boat in the driveway and the new battery is dead :( .

Hook up the charger give her a full charge and off to the lake again for some skiing. Boat starts and runs great

Sunday talk the CFO into just going up and floating around for a while. Starts right up and off to one of the coves for a float. After floating for a while I hit the key and it is dead again in the water this time Mad.gif .

Luckily the wind blew us over the marina and they give me there jump box. Well the jump box does not give me enough to start the boat. The owner tell me I more than a battery issue as he jumps lots of boat with the jump box all of the time. I convince him to let me use his charger in the shop. After a 20- 30 min charge the bu fires up :) I ask how does one check the alternator he told me to fire up the boat and disconnect the positive battery cable. If the boat dies right away then the alternator is not charging.

Got home fired her up in the driveway and disconnected the positive and the boat run for 15 mins before I turned her off.

Any other ideas on how to check the alternator would be very helpful.

Thanks again for all of your help!

Danadog

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Bought the top of the line battery charger ($80) at Lowes last weekend and it has a mode where you can check the alternator health. As well, this charger will charge batteries at 2 amps (small toys), 10 amps (Bigger toys), and 30 amps (real toys), then it also has an 80 amp option for directly starting a car without waiting for the battery to charge.

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You need specialized equipment to test for amps, but with an alternator usually if the volts are there the amps are good too. To test for volts, use a simple volt meter. First check the battery at rest, a charged battery should be between 12.5 & the low 13's. Start the engine & check voltage at the battery, if the alternator is working, the volts will be higher - mid to high 13's, if the alternator is not working, the volts will be lower than the at rest spec.

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Is your motor carburated?

Sounds like more than just an alternator problem. I've heard of the alternator test. But I don't think it applies to all boats. Try disconnecting the pos. cable while you have some accessories(stereo, blower, bildge pump) on. See if that changes things. You need an electrical draw for the motor to stop running. ??? maybe??? not sure

Were there any audio upgrades during the winter? anything else change over the winter?

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Has anyone heard of the disconnected the positive test before?

In theory, disconnecting the pos. cable and seeing if the engine dies, is a decent test but not 100% accurate.

When I was driving a tow truck and jumped a car, I would have the person immediately turn on all high power consumers like headlights, heater, rear defrost and see if the engine kept running. This would assure me that they would at least make it to a shop where they could have the battery and charging system tested.

If I were you, I'd think about taking the boat to that NAPA (and bring a fake a lake with you) and ask them if they'll test the charging system. It's really simple if you have the correct tools.

BTW, if you don't take it to NAPA, Hman's advice is pretty good too.

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Jasonk,

carburated motor

No audio upgrades besides speakers and installed a shower.

I will try turning on some accs to draw the power.

I bought the boat last Sept and only put on 14hrs before winter.

Put the battery backin this spring and it was dead.

Is your motor carburated?

Sounds like more than just an alternator problem. I've heard of the alternator test. But I don't think it applies to all boats. Try disconnecting the pos. cable while you have some accessories(stereo, blower, bildge pump) on. See if that changes things. You need an electrical draw for the motor to stop running. ??? maybe??? not sure

Were there any audio upgrades during the winter? anything else change over the winter?

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altenator should put out about 14 volts which can be measured at the battery cables with the boat running, also pulling the battery cable off is a pretty good test, sounds like your problem is elsewhere, I know you said your battery is new, but I would consider having it checked by an auto parts store for a dead cell, I have seen brand new ones not work for long.

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