Mercruiser 3.0 Not Charging

Hello All,
New to board and boating, this site is great for a newbie like me to get familiar with my new Starcraft (1977) Capri. Mercruiser 3.0 with a Mercruiser 140 Outdrive. Just bought it to take the family out on the water.

So here's my issue:
Noticed it yesterday with muffs on before we went out for the first time.
Engine cranked like it had low battery. Finally stopped cranking. I hooked up my truck and got er runnin.

Volt meter on dash shows 13 v while running, RPM doesn't affect it.
I left the truck on it and ran it for 1/2 hour or so at idle then shut it down.
I checked battery connections, removed and cleaned, retightened. Checked two connections on alt., looked good to go.

After removing cables from truck, restart engine. Volt meter shows 11 v...not good.

I checked at the battery with a voltmeter...12v
check 2 terminals on alt....12v

Something isn't charging.

I bravely pull out to go to the lake (kids are anxiously waiting and have lost their patience) but realize the importance of getting back after the day of boating.
Next stop Advance Auto. I pulled the alt. off and take it in..they say no problem...I was hoping to slap one in and be done.

Here is the info on the alt.

On top of casing it reads:
1102393 42A
76D20 12v Neg.


So I buy a marine battery to take with me (I'm not getting out of this trip.)

After cruising around Shenango Lake PA for about an hour and restart twice (once at dock, once after fishing) the battery isn't cranking the engine.
I pull out the new battery hook it up and we're back in business.

Volt meter still shows 11v after new battery install...no good. We decided to stay out for a little longer and head back.

I've never had a problem starting this boat, it just won't charge for some reason. By the way, the starter clunks a little when turning over usually when it fires.
Any help or ideas are appreciated.
Thanks,
Sean Swihart

Re: Mercruiser 3.0 Not Charging

Sounds like a mystery. The alternator only has the two connections? Sometimes they have a two wire plug and a seperate charging wire that bolts on(usually orange 10ga wire that attaches to starter solenoid). Ground is usually via attachment to the block.

Since you saw 13V on a votmeter, something might be charging.

Re: Mercruiser 3.0 Not Charging

Chris1956 said:

Sounds like a mystery. The alternator only has the two connections? Sometimes they have a two wire plug and a seperate charging wire that bolts on(usually orange 10ga wire that attaches to starter solenoid). Ground is usually via attachment to the block.

Since you saw 13V on a votmeter, something might be charging.

Click to expand...

test starter? when one item in starting system goes bad, check all items. I would check key switch as well.

Re: Mercruiser 3.0 Not Charging

just adding... when a starter's bushings wear, it will create drag as well as cause an open field. A sloppy armature will drain a battery and lead to destruction of your starting/charging system. Where as also in return... a bad alternator will lead to the destruction of a starter-switch-battery- or solinoid. When replacing one, check all.

Re: Mercruiser 3.0 Not Charging

Nobody caught the "off to autozone" I see..
But fyi...You never ever use an automobile alternator in your boat.
Marine rated with spark arresting screens and nothing else.

Re: Mercruiser 3.0 Not Charging

When you went to autozone did they only test alternator? you should only use a marine one with proper spark arrestors.(same for starter) If your alternator tests ok check wiring connections including any on voltage regulators if equiped. What is the voltage on the back of the alternator where large red wire is attached. Dou you have a bad connector between alt and battery? Have you done a load test on your starter? Do you have a local auto electrical starter/alternator rebuild shop to test/ repair marine components. These people specialise in this trade. I send lots of rebuild work to them because they stand behind their work.