21i draining batteries

[jchurch6713]

I have a 2001 21i that is draining batteries when sitting with everything off. I have disconnect the accessory wires on the battery and it still drains the battery so it must be somewhere in the engine connection. There are no visible shorts/chaffed wires and the drain is very slow it takes about 36 hours. I have tried three different batteries with the same result. I took the boat out last night and noticed that I was only showing about 10.5 volts on the gage and when I hit the taps button the rpm and speed gages would jump a couple notches and the battery voltage would drop off of the chart. I am showing about 11-12 volts when running about 30mph. Any Ideas? I have also had the common intermittent starting problem where sometimes all I hear is a single click and then nothing else. Could these problems be related?

[chpthril]

Sounds like your alternator has given up on ya. With all the accessory wires unhooked from battery and drain still present, that leaves the starter and alt and since the alt does not appear to be charging, that's my gut call.

Do you have access to DVOM (digital volt ohm meter) that will read amp draw also? It would be good to verify the alt output at the alt, and verify the drain as well.

[dogbert]

I'm with chpthril on this one. Mine went out last year on my '99. I'm assuming you have the Merc 315 Tournament Mag MPI?

[jchurch6713]

I am still confused about how the bad alternator will drain the battery when the boat is in storage. I can fully charge a battery, hook it up and never do anything else and the next day it will be dead. How would a bad alternator cause this?

[chpthril]

A shorted Alt will become a load and consume current when not in use.

If you can measure the draw, and then unplug the alt, you may see the draw drop to zero.

[lee]

I am still confused about how the bad alternator will drain the battery when the boat is in storage. I can fully charge a battery, hook it up and never do anything else and the next day it will be dead. How would a bad alternator cause this?

What are the volts when you say the battery is charged? What are the volts when the engine is running? You will need to check that with a volt meter not the gauge on the dash board.

[Fast1911]

You should also install a Perko shut off switch after you replace the alternator if you don't have one already. I put one in and it is awesome.

[jchurch6713]

I have replaced the alternator and have had no problems since. I appreciate all of the help guys.