Volt Questions

[sebber83]

My boat is a 1995 Doral Br185 (19 foot Bow rider) with an inboard 4.3 L Mercrsuiser LX.

Both batteries (starting and deep cycle) are brand new.

My voltage gauge never goes over 12.5ish and when I trim up or down it will dip as low as 9ish.

I am thinking the problem is my alternator. I had it rebuilt last year but I think the voltage is way too low. When I run other things like my stereo, ballast pump, blower, bilge etc, there is a dip in my voltage and it never goes back up until I shut down the accessory that I am running.

Any insight would be awesome before I spend the 220$ on a new alternator!

 

[trendsetter240]

Re: Volt Questions

With the engine off, connect a multimeter to the terminals on your starting battery. Observe the voltage.

Start the motor and let it idle. Observe the voltage.

Rev the motor up a few times to 1500-1800 RPM. Observe the voltage.

If you see no increase in the voltage when the engine is running then your alternator may be failed or not have a proper connection.

 

[sebber83]

Re: Volt Questions

Sounds like a plan, i'll get on that this weekend. But I am thinking more and more than when I got my alternator re-built last year they did a poor job of it. Should have saved the 150$ and gotten a new one! Live and learn!!

 

[NYBo]

Re: Volt Questions

Yep, you definitely have a charging problem. A fully charged battery reads 12.6v, and charging voltage is somewhere around 13.5 to 14.5 volts.

 

[sebber83]

Re: Volt Questions

Before I ran of and get the alternator, could it be anything else than the alternator? I checked the pulleys and belts and they are in tip top shape, checked my wiring and no visible damage? I will be more than glad to spend 220$ and solve my problem, but before I do, anything else to consider?

 

[JustJason]

Re: Volt Questions

why don't you spend 20 dollars and get a cheap multimeter.

 

[sebber83]

Re: Volt Questions

Already have one, I will run the tests... but I am trying to see if anyone else has any other ideas on what it could be, I figure its either my alternator or my gauge!

 

[dwco5051]

Re: Volt Questions

Did you replace any wiring when you installed the rebuilt alternator? I may be wrong but I believe this alternator needs a resistance between the ignition switch and the alternator. This is done in different ways depending on how yours was wired. It can either be a wire with built in resistance, a ballast resistor, or in some cases the idiot light bulb acts as the resistance. Something as simple as the bulb for the idiot light burnt out or the wire that should have a built in resistance replaced by a straight piece of wire can cause the alternator not to charge.

 

[NYBo]

Re: Volt Questions

Pull the alternator and take it to a shop for testing. Many auto parts places can do the test.

But don't buy an automotive unit if you need a replacement! (Bet you already knew that, though.)

 

[sebber83]

Re: Volt Questions

When the alternator blew apart last summer I just disconnected everything, brought it to the shop, had it rebuilt and then reconnected it using the same connectors and all. So if something in the wiring changed it was done by the shop. I will have to look into that! I am starting to think the shop rebuilt the core yet never looked at the internal regulator and that could be my problem!

 

[bruceb58]

Re: Volt Questions

Already have one, I will run the tests... but I am trying to see if anyone else has any other ideas on what it could be, I figure its either my alternator or my gauge!

For the amount of time it took you to come on here an type all these posts, you would already have your answer if you used you meter and measured.

Did you happen to use your meter last year before you took the alternator in to get it rebuilt?

 

[Boatist]

Re: Volt Questions

First off there is no resistance between the alternator and the battery.
The resistance 5051 is talking is for the ignition Coil and nothing to do with the alternator.

I do not see how you have both batteries connected as there are many ways.

If it is thru a switch I believe most alternators are killed by these switches.

If with the engine running you ever turn it thru off it will blow the alternator diodes.
If the switch is not a Make before Break type then turning the switch at all with the motor running will blow the alternator.

Any time the battery load is not on the alternator output it will blow the output diodes or the voltage regulator in a fraction of a second.
If someone were to pull the cable off the battery being charged it would also blow the alternator.

This is one reason I like to charge thru a battery isolator. To blow the alternator then you have to remove both batteries cables. However Isolator only work well with a properly wired 3 wire alternator.

A Fully charged 12 volt battery at a temperature near 70 to 80 degrees should read 12.6 volts. When charging with an I/O alternator even at 1000 RPMS the voltage should climb to 13.8 to 14.8 volts.

The way you voltage is dropping any time you add any heavy load is a clear indication that the alternator is not working.

Many type alternator but I believe the 3 wire alternators are the best as they charge better at low rpms. The one wire alternators seem to be becoming more popular.

Good Luck and report back what you fine.

 

[dwco5051]

Re: Volt Questions

Typical Delco wiring diagram.

 

[sebber83]

Re: Volt Questions

I've never see the indicator light, where would it be hidden? Took the boat out for a ride again yesterday, running with my battery switch on the dual position, so both batteries, I was still getting 12ish volts on the guage, and lower than that when trimming, running the bilge, etc. Once I got home, i put the charger on the batteries and they were both at the recomended voltage.

 

[Fl_Richard]

Re: Volt Questions

Sounds like you have added resistance to the wiring on your boat. This is usually a bad ground somewhere. I'd look over all the wiring you can see and connection points to the battery.

Flex the wires, listen for crackling inside or swelling on the outside. Both are signs of internal corrosion which means the cable is not passing current as effeciently as it should.

 

[dwco5051]

Re: Volt Questions

I've never see the indicator light, where would it be hidden? Took the boat out for a ride again yesterday, running with my battery switch on the dual position, so both batteries, I was still getting 12ish volts on the guage, and lower than that when trimming, running the bilge, etc. Once I got home, i put the charger on the batteries and they were both at the recomended voltage.

The indicator light is one of the possible ways of adding resistance to the circuit. It can also be a wire with built in resistance or a separate resistor. Do the two wires numbered 1 and 2 on the diagram go on separate terminals or are they a molded plug. If they are on screw terminals it is possible you have them reversed.

Forget about your dash gauge and check the voltage at the battery with a know good voltmeter. They should read about 12.8 when fully charged and the motor not running. When the motor is running above 1200 or so rpm the reading should climb to about 13.5 or 14 volts. If that happens you have a bad gauge.

If it doesn?t climb when the motor is running take the alternator to a parts store that can check it (usually for free) and see if it is the alternator.

 

[sebber83]

Re: Volt Questions

Perfect, thanks for the help. Only had the boat for a week before the alternator split in half last season, so I dont recall what the gauge used to read before that happened. I will follow the steps you guys told me to and see what happens. Thanks much!!!!

 

[180shabah]

Re: Volt Questions

It's a 15 year old boat, we ate forgetting the obvious. There is at least some corrossion on every connection on it. Add in a gauge that is rarely accurate.......

 

[Boatist]

Re: Volt Questions

Many shops can check your alternator for free. I do not know if the auto shops will have the charts to tell them which plugs to use to set up the test.

Your symptoms are exactly what you would see if either the voltage regulator or the output diodes are bad..

The voltage gauge sounds like it is working correctly. Of course check the voltage at the battery or the alternator 12 volt output line. The heavy 8 or 10 guage wire.

The voltage regulator and output diode blocks are not that expensive. I have not done one in about 10 years but at that time the voltage regular was under $10 and the output diode block under $20.
These parts usually the same as for an auto so many alternator shops should have the parts. The case parts that have the screen to prevent sparks from getting out have to be the marine version but those case parts should not fail.

I do not know about the mercury repair guide but the OMC repair manual has a step by step instruction to finding the problem and fixing.

 

[bruceb58]

Re: Volt Questions

I've never see the indicator light, where would it be hidden? Took the boat out for a ride again yesterday, running with my battery switch on the dual position, so both batteries, I was still getting 12ish volts on the guage, and lower than that when trimming, running the bilge, etc. Once I got home, i put the charger on the batteries and they were both at the recomended voltage.

Are you measuring these with a handheld meter?

Forget about the gauge! Use a meter until you know that the gauge is accurate.