Mercruiser 3.0 Not Charging

[swihartart]

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.
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

 

[Bondo]

Re: Mercruiser 3.0 Not Charging

Ayuh,... It's gotta be either the Alternator, the Voltage Regulator, or the Wiring...

You should be seeing 13.6 Volts when runnin'...

 

[swihartart]

Re: Mercruiser 3.0 Not Charging

Thanks for posting Bond-o.
Where do I find the VR and can it be tested with a meter. I'm trying to look up a manual for this system but They've been removed or kicked to Merc's website.

 

[Bondo]

Re: Mercruiser 3.0 Not Charging

Where do I find the VR and can it be tested with a meter.

Donno,... You haven't said Which alternator you've got,... There's been several used over the years...

I'm trying to look up a manual for this system but They've been removed or kicked to Merc's website.

There's a locked thread down at the bottom of page 1, or possibly on page 2 that explains the "Work Around" for the Issue...

 

[swihartart]

Re: Mercruiser 3.0 Not Charging

Here is the info on the alt.

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

 

[Don S]

Re: Mercruiser 3.0 Not Charging

The part number on the alternator isn't going to help much. Since 77, that alternator may be completely different from the one that came on your engine.
If you go up to the Adults Only sticky at the top of the forum, you can download the OEM manual for your engine. There is a section in it on alternators, along with pictures of the ones used on your model. There are also troubleshooting instructions for the charging system with the alternator on the boat.
You could also just take the alternator to a starter/alternator repair shop in your area and have it checked out and repaired.