Alternator upgrade question

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-05-2006, 5:23 PM

I'm thinking that my boat isn't getting good enough voltage from the alternator. My Perfect Pass will show low voltage alarms if I turn on too many electrical components. I did a search through the archives and got plenty of info. on the charging system.(Thanks Rod and Grant). I would like some input on what route to take in purchasing a new marine alternator. I thought I remember Grant saying that he bought one and it didn't have the screens on it to make it marine. I have a 92 Nautique Excel with two medium sized amps,two tower lights,three ballast pumps,heater,shower,and Perfect Pass. I have no idea if I need a HO alternator or just a new 50 amp. Any info. is appreciated.

(kody_a) · (kody_a) **Join Date: Aug 2005** 06-05-2006, 6:05 PM

When exactly does the alarm sound. Also is there a specific thing that you turn on that sounds the alarm.

good luck

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-05-2006, 8:39 PM

I think around 10.5 volts. Depends on the system voltage when I turn on the other items on if it drops to 10.5.

(peter_c) · (peter_c) **Join Date: Sep 2001** 06-05-2006, 9:07 PM

Nautiques have a known problem with a lack of amperage flow to the dash components. With a digital volt ohm meter, check the battery voltage, then test the voltage at the components. This is going to be done with the boat running after warming up the alternator and everything on that you usually use.

In my own boat I had to run a new power feed wire to the circuit breakers.

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-05-2006, 9:09 PM

Peter,
I already did that. I ran a #4 cu. to the dash. I forgot to mention that. Thanks

(peter_c) · (peter_c) **Join Date: Sep 2001** 06-05-2006, 9:13 PM

Ok so what is the battery voltage (Not the guage) when PP starts beeping?

(kody_a) · (kody_a) **Join Date: Aug 2005** 06-05-2006, 10:24 PM

Has it just been recently?

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-06-2006, 5:54 AM

Starts beeping at 10.5-11 volts.

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-06-2006, 5:56 AM

Been doing it for about a year now. I didn't realize how bad it was for the battery and system until I read the archive articles.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 06-06-2006, 7:04 AM

talk a rebuild shop yrour old alt, and have them just rewind it, you can get a very strong 90-105 amp for around $50-60. My experience is that if you want bigger than a 105 and want it to last expect to pay $300-400+. Make sure you let them know it's going in a boat. your boat at idle is proabbly putting out 5-10 amps max and only WOT is getting the 50 amps (if that), your boat is starved for power. Have you bench tested your current alt?

(peter_c) · (peter_c) **Join Date: Sep 2001** 06-06-2006, 8:21 AM

Rod, is that 10.5-11 volts at the battery? How does the boat restart? Because with that low of a voltage it shouldn't.

(lukeduke95) · (lukeduke95) **Join Date: May 2002** 06-06-2006, 9:11 AM

He just means that is what he gets at the dash. With the pidly wire they have to run all of the gauges and power everything, the voltage drops down a bit.

Mine does it to, but I still get full votage to the starter.

mia 06-06-2006, 10:16 AM

what are you using for batteries and how many ?

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-06-2006, 4:33 PM

Peter,
That is at the Perfect Pass which coincides with the in dash volt meter pretty well. When the battery (Optima Blue Top) was new, it had no problems. Now it won't restart the boat. I even replaced the Optima with my battery from my house boat and it's doing the same thing. The Perfect Pass used to beep for a few minutes when I first started the boat, now it is constant and the voltage goes between 10 and 11 volts.

(peter_c) · (peter_c) **Join Date: Sep 2001** 06-06-2006, 5:25 PM

Take a real digital volt meter (Not something mounted in the boat) and after running for a couple of minutes to warm up the alternator check the voltage at the battery, then right off the back of the alternator. You should see 13.7-14.3 at about 1000 rpm. Check all connections including the battery cables, grounds, and alternator wiring. Replacing parts because of an improper diagnostic is not the way to fix things. Test don't guess!

As said above you could pull the alternator and have it bench tested. Easier to do it in the boat though under live conditions which also tests all the wiring.

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-06-2006, 8:14 PM

Thanks Peter,
I have a Fluke 57 and free launches 10 minutes away. You are exactly right, I'll put it in the water tomorrow and do some voltage reads from the alternator to battery. Thanks for your input, it is appreciated. I'll post the volt reads tomorrow night.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 06-07-2006, 6:26 AM

your running all this on a measly 50 amp alt....I have a 92 Nautique Excel with two medium sized amps,two tower lights,three ballast pumps,heater,shower,and Perfect Pass. My experirence with older marine alt's is that most are junk and don't even bench at what they are rated at. That alternator is 14 years old. Based on the other posts you've made , I'm guessin your alt is shot. I'm curious to see the voltage results.

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-07-2006, 9:16 PM

Adam.
I went to my nephews baseball game today. I will do the voltage reads tomorrow and post. Thanks.

(rvh3) · (rvh3) **Join Date: Jul 2003** 06-10-2006, 2:34 PM

OK Peter,
You were right, test don't guess. I got 14.35 volts at the alternator, 14.27 at the battery and 12.7 at the ignition. Then 10.7-11.3 on various dash guages and my PerfectPass. I have a bad neutral wire behind the dash somewhere. The reason I ruled that out before is that I thought I wired my perfect pass to a separate feed from the dash. So, with the PerfectPass and the dash volt gauges showing low, I deducted it was low from the battery. Problem was that I pulled my neutral for my PerfectPass from my dash. Now I get to go through the rats nest behind the dash to find the bad connection. Thanks again for your input.