Help with overcharging boat

[Chris142]

I guess this should go in this forum. A friend of mine has a larger fishing boat. It has a 350 Chevy engine in it. The Alternator is not your standard GM Alternator. It has an externally mounted voltage regulator that also holds the brushes.

It's a marine type with screens to prevent an explosion and what ever else they require for marine use.

The thing overcharges the battery......17+volts which burns up the electric fuel pump and light bulbs.


We replaced the Voltage Regulater with a new one and it still does it. Cleaned grounds etc.

It has a wire that I assume tells the regulater what the voltage is.I ran that straight to the battery. Still overcharges. I also ran a new ground wire from the Alternator to the battery and it still overcharges.

The Alternator tests fine on the bench. Any ideas? We want to go fishing.

PS: It's an Aquasport 215 with a Volvo Penta outdrive.

 

[tomcat27]

just to clarify - when bench tested, did the alternator read the proper voltage?

 

[The_Eric]

Is it any of these types?

 

[Chris142]

Originally Posted By: tomcat27
just to clarify - when bench tested, did the alternator read the proper voltage?
Yes it works fine on the bench..13.8-14.2 volts. Don't remember the amperage out put but it was normal depending on the load we put on it.

 

[Chris142]

Originally Posted By: The_Eric
Is it any of these types?
I don't remember which one. I printed that out and am heading over there now. Thanks for posting that!

 

[Carbon]

I suspect there is a broken connection. Could it be that the regulator was designed with the expectation that the case would be grounded? Try running a ground to the case. If that does not solve it, check if any of the wires are broken.

 

[Chris142]

its the late mando style alt. thr battery referance post has low voltage. too much resistance somwhere? I ran a wire from it to the battery and it works fine

 

[Chris142]

I should say that it charges fine but we need to find the reason for the voltage loss. My jumper gives the alt a good battery voltage referance but causes other problems such as it runs even after removing the key

 

[mechtech2]

Weird that it would bench test OK and run so high when installed.
Clean both ends of all power and ground cables and where they seat - nice and shiny. Maybe an additional heavy ground wire.
It's what I'd do next.

 

[Kruse]

Base of the regulator lost it's ground, somehow.

 

[Chris142]

Originally Posted By: Kruse
Base of the regulator lost it's ground, somehow.
Ok it got too hot so we quit. The Alternator gets it's 12v referance from a wire that comes from the ignition switch.

The battery voltage is say 12.6 but the wire that tells the Alternator what the voltage is only shows say 10.5 volts. So since the battery referance is low the alt boosts the out put voltage(and prolly amps too but I don't have an ammeter) untill the referance is 12.xxx or higher.

Theres correct voltage at the breakers. From the breakers the wires run inside the wall of the boat to the switch. Power is low at the switch.

I ran a jumper from the battery to the referance post on the alternator and the thing charges like it should. Take my jumper off and it overcharges 16+volts.

I'm guessing that somewhere in the wall of the boat is a dirty or loose connection. But I can't find it with out taking 1/2 the boat apart.

 

[The_Eric]

Yeah, boats can be fun like that.

 

[1 FMF]

Originally Posted By: Chris142
Originally Posted By: Kruse
Base of the regulator lost it's ground, somehow.
Ok it got too hot so we quit. The Alternator gets it's 12v referance from a wire that comes from the ignition switch.


if the reference is coming from the ignition switch key on, then that's indicating the ignition switch is going bad and the resistance is in the contacts of the switch. That is typical of a boat ignition switch especially one that's exposed and gets hit with rain. The best fix would be running the 12v reference wire as close to battery + as possible since the whole purpose is to prevent battery overcharging/over-voltage.
as for the ignition switch if the wire from it on the IGN side is going to a relay then you can live with the resistance as long as the ignition relay/solenoid activates. However if that IGN wire from the ignition switch goes right to the + side of the ignition coil then your ignition is not getting full power and you should either (a) replace the ignition switch or (b) install a relay to ensure the coil gets full voltage.
also check the throttle/shifter if there is an ignition cutoff switch, the kind you're supposed to have a lanyard hanging off of attached to yourself...

that switch can go bad and be the resistance in the circuit causing problems.

 

[mechtech2]

Those wires are supposed to have some resistance in them - From the light or by design.
but if a straight wire fixes it, OK.

 

[Donald]

First let me say the Mando is a decent alternator until it breaks, but then don't bother getting it rebuilt, as the rebuilders HATE them. Its Korean and used on Mercruisers and Bobcat loaders. I replaced mine with a local rebuilt Delco and it runs fine (when the boat actually gets into the water).

The alternator has 3 wires coming off it besides ground. The larger one goes to the battery as output from the alternator.

The red wire (sense) goes to the battery, it does not draw any current so it does not need to be switched via the ignition switch. I assume its fused somewhere. There should basically be zero voltage drop on that wire from the battery to the alternator connector.

The purple or black is the excite wire. It must be switched via the ignition switch or it will drain your battery when the engine is not running. Power from it is used to excite the windings in the alternator and how much they get excited is controlled via the voltage regulator as sensed from the sense wire. How much the windings are excited controls how much charge is put out.

If you swap the excite and sense wires by accident, the alternator will charge fine, but the battery will die when the engine is not running and the alternator may be warm to the touch until the battery is dead.

Does the boat have a battery isolator and 2 or more batteries?

I would check the voltage at the alternator with a DVM from the red wire connector to the alternator ground, also to the neg battery post and compare it to across the battery. Hopefully they are all exactly the same.

 

[Donald]

Originally Posted By: mechtech2
Those wires are supposed to have some resistance in them - From the light or by design.
but if a straight wire fixes it, OK.


Not on a Mercruiser.

 

[meep]

bad connections and boats go hand-in-hand. sorry you have to take 1/2 the boat apart to find the culprit, but that's how they are. if the ign sw turns out ok, it could be any other conenction or switch in the circuit. Or there could be a seized pump or other device pulling too much current somewhere. Typical pleasureboat marine wiring can be a hack, even in surprisingly "high end" boats. Example-- as much as we ding chrysler for [censored] electronics, a chrysler wiring harness quality is far beyond a searay. ask me how I know.

IF you can't track it down, use a relay. drive the relay by the ign sw and use it to switch that alt ign lead on/off from the battery. It will have its own run to the batt, and will still be switched. make sure the relay is marine rated for spark arrest.

Yes, 17V is pretty darn high.

good luck!

m

 

[Chris142]

The boat has 1 battery. I have not had it load tested but it cranked that Chevy over for a good minute so I think the battery is good.

Voltage at the ign switch is the same on both sides of the switch so the voltage drop is between the battery and the switch.

 

[Donald]

Originally Posted By: Chris142
The boat has 1 battery. I have not had it load tested but it cranked that Chevy over for a good minute so I think the battery is good.

Voltage at the ign switch is the same on both sides of the switch so the voltage drop is between the battery and the switch.


The sense wire does not get switched, it should be going directly to the battery with a fuse. Not saying you don't also have a voltage drop to the switch, but read my first post again and follow what I said.

Isn't there also a big round harness connector, that can be pulled apart and reseated.

 

[meep]

odd that it seems to be sensing from the exciter wire rather than the sense wire. Admittedly that will be harder to troubleshoot over the 'net.

But at least you know the resistance is upstream of the ign switch.

2 volts is a pretty severe drop. I'm suspecting corrosion in a physical connection, such as a crimp connector or fuse.

you could still use the relay idea but the cause of the problem will still be lurking. you'd want to find it... getting stuck stinks.

Can you pull an amp measurement off the ign switch to see if it's an overload?

M