[aaron41]

i like to change the alternator in my boat to a new one.
any recommendations ?

 

[Faster]

Need more info.. which engine, how big a battery bank? What are your needs (ie refrigeration? inverter? microwave?)

 

[weinie]

why change it?

 

[aaron41]

the old one is dead. i have 1 bank of 2 batteries. need the batteries for starting the engine, lights, VHF, charging phones and tablet, etc.

 

[GeorgeB]

Aaron, still not enough info. Electrical charging systems can go from pretty basic to pretty complicated – in a hurry. What do you have now? What is your engine size? (and make) Does your C27 have an internal (Diesel or gas) engine or outboard? What are the battery sizes? My guess (based on no factual information) is you have a stock, “Motorola” style alternator that is internally regulated. You will want to replace it with one that has the same specs and bracket (foot) size. You will also want to know why you “fried” the last one. Did you move the battery selector switch while the engine was running? You may also want to invest in a spark arrestor too. You will also want to spend a day (or two) running down the wires on your boat and making a wiring diagram. This will go a long way if you have a problem in the future.

 

[JimsCAL]

Are you sure its one bank with two batteries and not two batteries with a 1-2-Both-Off switch? And how did you diagnose the "dead" alternator? And tell us the make and model of the engine.

 

[aaron41]

you are right. it is 2 batteries and 1, 2, and both switch. i connected the alternator to my table saw electric motor, run it and checked the output with multimeter. the reading was 0 volt.

 

[Maine Sail]

you are right. it is 2 batteries and 1, 2, and both switch. i connected the alternator to my table saw electric motor, run it and checked the output with multimeter. the reading was 0 volt.

Was there a battery involved in this test?
Did alt B+ go to battery + and the case grounded to battery - ?
Is the alt self excite?
If not did you power the exciter wire?

As others have said we need way more information that you are giving us in order to help you...

Zero volts only tells us you did not do a correct or valid test on this alternator. You simply can not test an alternator with 0V. At a bare minimum you should have at least seen battery voltage of 12V+. In order to test an alternator there must be a load/battery present...

 

[aaron41]

this is the original alternator and i think it is self exciter.
i did not connect the alternator to the battery, but in fact i had a reading of 2 - 3 volt. i have a dead battery that i can connect to the alternator and retest the alternator.

 

[aaron41]

i retest the alternator with a dead battery and i still have a reading of 2-3 volts.
i received a new alternator - delco 110 amp 3 wires 12v, and when i am testing the alternator with no battery i get 27v. when i connect the battery and run the test, i get 0v.

 

[tommays]

Your doing something wrong as i am not sure how you would get any reading without proper connections let alone 27

 

[GeorgeB]

Aaron, a 110 Amp alternator is going to rob a significant amount of horsepower out of what I'm assuming is an 18 HP engine. And it probably is overkill given a Group 27 battery bank. This will also manifest itself in poorer fuel economy. I experienced a drop in fuel economy when I went to a 120 Amp externally regulated alternator running on my 35 HP engine. So much that I'm looking seriously at swapping out to a 90 Amp alternator.

 

[Maine Sail]

Aaron, a 110 Amp alternator is going to rob a significant amount of horsepower out of what I'm assuming is an 18 HP engine. And it probably is overkill given a Group 27 battery bank. This will also manifest itself in poorer fuel economy. I experienced a drop in fuel economy when I went to a 120 Amp externally regulated alternator running on my 35 HP engine. So much that I'm looking seriously at swapping out to a 90 Amp alternator.

George,

Just drop the max field potential in Balmar's Belt Manger and you'll have your 90A....

Aaron41,

I really don't think I can continue to help you if you won't help yourself.

If you want help understand this not texting, we have asked for more specific information (DETAILS) and are continually met with one sentence responses and no detail at all..

At this point all I can say is that you apparently don't know what you are doing, may cause damage the new alternator and I would strongly suggest you seek out an auto electric shop to test both of your alts. They usually won't charge you anything just to test them...

Either give us a LOT MORE INFORMATION so we can help, or seek out a professional...

 

[norahs arc]

If your engine is an Atomic 4 like mine just get the alternator you have checked out and repaired if necessary.

AND THEN check that the wiring harness plug in the engine compartment is making a GOOD connection from the alternator to the amp meter. This was a weak link in my own system - damaged the regulator, got that replaced (for under $200.00 cdn) and then ran a new wire from the alternator output to the battery bank with a new amp meter in the line.

I use more electric power than you do and the 37 amp output is more than enough running the engine in and out of the marina and the odd power trip around when the wind is not cooperating.

 

[GeorgeB]

Mainesail, Can I do this on an Amptech alternator and Xantrex external regulator? I do have the "small engine switch" - Do I continue to use that? (PITA to be continuing switching back and forth)

 

[Maine Sail]

Mainesail, Can I do this on an Amptech alternator and Xantrex external regulator? I do have the "small engine switch" - Do I continue to use that? (PITA to be continuing switching back and forth)

The alternator does not matter because it is the regulator that controls the field.... It depends which Xantrex regulator you have. If it is the Xantrex XAR then it is made by Balmar...

I believe on the XAR they still refer to it as Amp Manager. This is your field control and you can dial back the output to what ever you desire.

 

[MarkSF]

i retest the alternator with a dead battery and i still have a reading of 2-3 volts.
i received a new alternator - delco 110 amp 3 wires 12v, and when i am testing the alternator with no battery i get 27v. when i connect the battery and run the test, i get 0v.

Don't run the alternator without a battery as load! You can damage the diodes.

 

[travlin-easy]

Don't run the alternator without a battery as load! You can damage the diodes.

You will blow the diodes if you run it without a load.

You can get an alternator repaired for under $100 at any alternator/generator/starter repair shop. They do a good job and installation is easy on a Catalina 27 powered with an A4.

Gary