First post, lots of info. 1981 Formula Mercruiser 350 voltage issues

1981Formula

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Joined
May 2, 2012
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3
Hey folks, you have a great site here I just registered and have already learned a bunch.

My friend and I bought an '81 Formula 233SC I believe is the model of it, it's a 23.5' Formula with a 350 Mercruiser I/O. We got it for dirt cheap because it was basically left in a field to rot. Interior was rotten from rain coming in from a hatch that was never repaired, etc....

Anyway, found out the engine was bad with a cracked block and cracked heads, manifolds were shot as well. The engine was redone by a machine shop and the carb was rebuilt, new manifolds, new risers, two new batteries. The previous owner said the alternator was new but knowing this guy, it's an alternator for a chevy truck. Would that still work or no?

The problem we are having is that shorepower doesn't seem to be charging the batteries very well and the alternator is definately not charging them because I got stranded out on the other side of the lake today with two almost dead batteries. For example, when I got back to our slip finally I tested both batteries and both read 11.47 volts, I hooked it up to shore power for an hour and both read 11.89 volts. Then I was using the radio and a couple 12v lights and about an hour later they read 11.4 volts. Now I would imagine shore power would more than keep up with a couple lights and a radio wouldn't it?

Is there a regulator on the alternator and inside the 120V part of the boat or just one somewhere? Is there maybe a common issue that I am just not familiar with because I am pretty new to these types of boats. I know the groud wire coming from inside the control panel of the cabin that goes to the battery is pretty thin, likely done by previous owners because it looks too thin for a good ground.

Sorry for the long post, we have spend 8 months and lots of money bringing this boat back from the dead and are so close to having something we can take out and have fun, these last little problems are confusing me so any help or direction would be great.
 

tpenfield

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Jul 18, 2011
Messages
19,188
Re: First post, lots of info. 1981 Formula Mercruiser 350 voltage issues

Welcome to iBoats:

Just a couple of points . . .

The fuel, electrical and ignition systems on a boat must be marine certified. That is because fumes from fuel cannot readily escape the engine compartment and can reach explosive levels. The marine certified systems are designed not to allow fuel spillage and also not to throw sparks. Look for SAE J1171 tags on the starter and the alternator, etc.

So, if the alternator is from a truck, is is not safe and should be replaced.

Second thing is that with a boat of that age and one that has sat outside, the structure below should be examined for rot, if you have not done that already. Also, the fuel tank, may have a lot of corrosion and could leak through. So, those things need to be checked out if not done already.

Post some pics of your boat.

I am currently working on some issues with my 1991 Formula, so check out the links in my signature below, if you are interested.
 

1981Formula

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Joined
May 2, 2012
Messages
3
Re: First post, lots of info. 1981 Formula Mercruiser 350 voltage issues

Thanks for the tips. I will post some pics here in a bit.
 

1981Formula

Recruit
Joined
May 2, 2012
Messages
3
Re: First post, lots of info. 1981 Formula Mercruiser 350 voltage issues

Here are some recent pics. Just put the boat in about five days ago.


1002514r.jpg


1002505a.jpg


1002509m.jpg


Rear seat has seen better days but will be rebuilt. This was taken on her first trip in the water in probably 5 years or more thanks to the worthless previous owners...
1002508kl.jpg
 
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