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Replaced alternator - boat won't shut off


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My boat has the Leece Neville 51amp alternator on it.  Since it is a LS1, it has the serpentine belt system instead of the V-belt most Malibu's had at the time.  It failed right after I bought it; that one failed soon after a rebuild, I was in the middle of a season and just bought another so I could get on the water quickly.  I've been running it since 2012 but the bearings are getting increasingly noisy.  I also know it is not really up to the task of what I put it through, so an upgrade was in order.  

Bought this alternator:
https://smile.amazon.com/gp/product/B0081SE1CG/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

And this weather pack connector:
https://smile.amazon.com/gp/product/B01HOVW77Q/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

Bolts right up - a little tight but no grinding needed.  I upgraded the wiring to 2awg for power and ground off the alternator.  Belt is close but it fits.

Hook it up, all works except the BOAT WON'T SHUT OFF.  Ignition off, kill switch pulled, batteries turned off...doesn't matter, stays running (on the hose in the driveway, luckily).  I have to stall the motor by turning the fuel valve to the tank off to kill it.  After some research, I deemed it was an internal diode on the alternator, and figured this was the case as the first unit I bought was a bit questionable when it arrived (off of eBay, didn't seem brand new).  Then I bought the one on Amazon, tried it this morning with the same result.

I can confirm the purple (ignition) wire is 12V on, 0V off...checked several times.  I can also confirm that if it isn't hooked up the alternator will NOT charge and boat shuts off fine.  Only when it starts charging is there the issue.  

I confirmed with this wiring diagram that the 3rd pin from the left (when the connector tab is at the top, looking at the alternator) is the ignition pin, and that's what the purple wire attaches to.

http://www.delcoremy.com/documents/alternator-instruction-sheets/installation-instructions-for-replacing-connector.aspx

I'm at a loss here.  Either I got two bad alternators, from two different vendors, or I've got something wired wrong...and there isn't exactly a pile of wiring here!  As a side note, swapping back the old alternator and everything works fine.

Edited by Nitrousbird
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Sounds to me like the purple wire is connected to the wrong terminal.  The alternator will push a 12v signal down the line on the I post.  Since that connects to the "run" side of your keyswitch, there's a constant 12v signal on that keyswitch terminal so even after you turn off the keyswitch, that post stays energized and the boat stays running.

Try bridging together the I and the S posts to the purple wire.

Edited by UWSkier
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32 minutes ago, UWSkier said:

Sounds to me like the purple wire is connected to the wrong terminal.  The alternator will push a 12v signal down the line on the I post.  Since that connects to the "run" side of your keyswitch, there's a constant 12v signal on that keyswitch terminal so even after you turn off the keyswitch, that post stays energized and the boat stays running.

Try bridging together the I and the S posts to the purple wire.

I would have to buy a new hardness as this one is only designed for the two wires (other two are blocked out).  

11si.jpg

Sense wire shows optional.

Edited by Nitrousbird
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6 minutes ago, UWSkier said:

You can try putting a diode inline to prevent back-feeding the 12v potential to the key switch.

This.  I'm not sure how much current it will need, so measure from I to ground and I to B+ your alternator with an ohm meter with the harness disconnected.

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8 minutes ago, UWSkier said:

You can try putting a diode inline to prevent back-feeding the 12v potential to the key switch.

 

Just now, justgary said:

This.  I'm not sure how much current it will need, so measure from I to ground and I to B+ your alternator with an ohm meter with the harness disconnected.

I was thinking the same thing.  Just ordered this:

https://smile.amazon.com/gp/product/B07XWXFV34/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I figured a 20A diode should do the trick, as the purple wire is probably a 16-18 awg wire (easily fits in a red butt connector, as does the harness wire).  Probably overkill but why not for the price?

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1 minute ago, Nitrousbird said:

 

I was thinking the same thing.  Just ordered this:

https://smile.amazon.com/gp/product/B07XWXFV34/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I figured a 20A diode should do the trick, as the purple wire is probably a 16-18 awg wire (easily fits in a red butt connector, as does the harness wire).  Probably overkill but why not for the price?

That ought to do.  Put the silver band toward the alternator.

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Diode installed and it worked!  

Voltage is higher than expected.  My old alternator(s) always had low voltage, typically in the mid 13v range on the dash.  This one is at a steady 14.8 - 14.9 on the dash at idle (I gave it some gas too - no change).

Too my DMM and measured 15.3 at the alternator (fluctuating from 15.27 - 15.34).  At the battery, a solid 15.19.  Oddly, at the helm, which is only 2awg from the battery, going through a fuse link, it is 15.18...much less voltage drop than I would have figured.  Obviously the digital volt meter on the dash is low (or my DMM reads a bit high...it has seen some use over the years, so quite possible).  00 awg from the starter to the batteries; I'm sure the voltage drop is at the starter.

I'll have to research whether that voltage could have any long term consequences being that high.

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Got a buddy with another DMM you can check?  My alternator from DB came with a full test bench report and a validated 14.0 setting on the Voltage Regulator, which is bang-on what I measure with a good battery charge.  FWIW, my dash reads a bit low also.  My PerfectPass will say 13.7v when my dash gauge is right around or shade above 13v.

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7 minutes ago, UWSkier said:

Got a buddy with another DMM you can check?  My alternator from DB came with a full test bench report and a validated 14.0 setting on the Voltage Regulator, which is bang-on what I measure with a good battery charge.  FWIW, my dash reads a bit low also.  My PerfectPass will say 13.7v when my dash gauge is right around or shade above 13v.

Yes, I have access to other DMM's - will likely check with a different one this weekend.

Spec sheets shows it is putting out way more current than rated.  95amp alternator, 113amp max, the curve hits 100amp @ 3200 RPM.  Voltage set point is 14.65V, with a secondary regulation at 15.62V.

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Same here on the over-spec current, but my voltage is bang-on so far.  Test report on mine showed 90 or 95 amps also at fairly low RPM.  Keep in mind also, the alternator spins much faster than the engine so 3200 RPM on the alternator is probably less than half that on the tach.

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3 minutes ago, UWSkier said:

Same here on the over-spec current, but my voltage is bang-on so far.  Test report on mine showed 90 or 95 amps also at fairly low RPM.  Keep in mind also, the alternator spins much faster than the engine so 3200 RPM on the alternator is probably less than half that on the tach.

Yeah, I was aware.  Mind you, my previous alternator was undercharging and I would see severe voltage drops running my ballast pumps.  It just wasn't designed for what I was pushing it to do.  I run two Group 34 AGM batteries and a 20 amp dual bank onboard charger that the boat sits on 24/7 in the garage.  That said, I am still killing batteries every 2-3 years even with the charger.  I just increased my drain adding a new pump, which was why I wanted a bigger alternator (along with needing a replacement), as I refused to run all my pumps at once on the stock one.  .

1 minute ago, UWSkier said:

BTW I have to think >15v to your batteries with any regularity for extended periods will not end up with them enjoying a long happy life.

My thoughts too.  Also why I want to check my DMM as it may just be reading high, as I'm not seeing that on my digital readout on my gauge, at it is powered only a few inches from where I am reading off the helm.  I swear, nothing is easy with my projects...

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15 minutes ago, justgary said:

What does the voltage do if you connect the sense wire to the battery (or maybe the starter lug)?

We are not there yet.  After the holiday weekend if my buddy's meter reads high, I will trying that next.

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