Leece Neville 90amp Alternator Upgrade

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WindEnsemble's picture
WindEnsemble
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Leece Neville 90amp Alternator Upgrade

Just need a sanity check. I upgraded the alternator to the Leece-Neville 90amp 8MR2069TA with the stock 8RG2043 regulator. Fits perfectly as a direct replacement for the original 55amp alternator. The only difference being that the new alt. is "self excite" and so the exciter wire is not connected. I left it in place (tied off out of the way) since I plan on keeping the old alt. as a backup. So, the positive out post is connected to my house battery and the tach wire is connected to AC Tap. There are 2 posts on the regulator labeled AC Tap, so I assume it doesn't matter to which I connect. Anyway, I am not getting a reading on my tach, nor do I appear to be getting any output from the alternator. That is, the volt meter is not showing "charging". The batteries were showing 75% prior to starting the engine. I have not actually measured with my DVM. Am I missing something?

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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newguy
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These are self-exciting alternators, so should be plug and play.  Yes, the AC tap connects to your tachometer and it does not matter which one.  Suggest you do the following first:

  • Engine not running and ignition off
  • DVM to 20 volts DC scale
  • Make sure the NEG terminal is connected to the engine block.
  • Measure between the POS and NEG terminals on your alternator.  You should be reading battery voltage.
  • Measure between POS and NEG terminals at the battery that the POS wire from the alternator connects to.  You should be reading the same voltage (+/- a few millivolts)
  • Start your engine.  Measure between POS and NEG terminals at the battery.  You should now be reading a higher voltage than you read before.

A bit of caution.  In most installations, the POS output of the alternator is not fused.  Take all necessary safety steps when working with non-fused circuits.  Also, don't be taking measurements on the alternator while the engine is running unless you are very confident with working around rotating machinery.  Those pulleys and belts are unforgiving of mistakes.

Nick Caballero
Retired C36/375IA Mk II Technical Editor

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WindEnsemble
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Thanks, Nick. We wondered about the ground, but the NEG post on the previous alternator was not specifically grounded to the engine, so we did not connect this one. Of course there appears to be no definitive source for how to connect these new alternators. At least we could not find one.

We did all of your other bullet points, though just using the volt meter on the switch panel rather than the DVM. I realize it's not as accurate, but it's always been obvious before when charging is actually occurring. Of course, the zero reading from the tach was the primary tell that there was a problem.

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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newguy
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Some alternators use the case as ground and the mounting hardware is the ground path.  Some alternators use an "isolated ground" and you have to supply a separate ground for them.  So, on alternators that provide a ground lug, always connect a ground cable here as large as the POS cable being used.  Naturally, I'm assuming that your battery banks are grounded to the engine....

The reasons why I suggested using the DVM at the various test points is both for diagnostic purposes as well as to to eliminate some other variables.  May I suggest that you go ahead and wire a ground to the alternator's NEG terminal, take the readings in the sequence indicate earlier, and send back those readings.

Nick Caballero
Retired C36/375IA Mk II Technical Editor

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WindEnsemble
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[quote=newguy]Naturally, I'm assuming that your battery banks are grounded to the engine....[/quote]

You assume correctly.

[quote=newguy]May I suggest that you go ahead and wire a ground to the alternator's NEG terminal, take the readings in the sequence indicate earlier, and send back those readings.[/quote]

I will do that later today and post the results.

Thanks,
Jeff

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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WindEnsemble
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[quote=newguy]May I suggest that you go ahead and wire a ground to the alternator's NEG terminal, take the readings in the sequence indicate earlier, and send back those readings.[/quote]

Pre-start:
Voltage at alternator POS/NEG lugs: 13.47
Voltage at battery: 13.51

Post-start:
Voltage at battery: 14.40

And the tach works!

Thanks for the help!

Jeff
 

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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WindEnsemble
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[UPDATE: See my note below.]

Going to add one more post here in hopes that it might help someone who may be considering upgrading to the 90 amp alternator. We decided to upgrade when our current alternator failed. We got it repaired to keep as a backup and ordered the new 90 amp model. The only identifying information on the old alternator was "A-9249". Everything else has been painted over (ugh!). It appears this cross references to a Leece-Neville 8MR2049KA (51 amp). The new alternator is a Leece-Neville 8MR2069TA (90 amp). As noted before, the new alternator was a direct replacement (NOT...see update below). No modifications were necessary (yes they are!) to install/get the belt to line up. Also, our boat has the M25XP motor which already had the bracket upgrade.

Please refer to the attached pictures. 

Wires connected on the 8MR2049KA:
Exciter
Tach
​POS out to house bank
No ground wire connected. This alternator was getting its ground through the case (Thanks Newguy and Maine Sail).
(Please note, the regulator pictured is a new regulator. I have no idea what the original regulator model was)

New alternator:
This alternator is "self-excite", so no exciter wire connected
Tach connected to "AC Tap"
POS out to house battery
NEG post to ground, through the ground post on the engine block. (As pointed out by Newguy, the lack of this connection was the source of my problem)

 

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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Maine Sail
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Some of the Leece-Neville 8MR series alternators are case grounded and others are isolated ground. A quick continuity test with a multi-meter between the ground stud and a bare part of the case will tell you which type. If you have continuity it is case ground no continuity and it is isolated ground. Leece-Neville is not good about calling this out in their documentation but a DVM will tell you the answer in about two seconds....

-Maine Sail
https://www.marinehowto.com/

 

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HowLin
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I assume that it will also direct replace on an M35B also?...

---- Howard & Linda Matwick ----

--- S/V "Silhouette" - Nanaimo, BC ----

--- 1999  C36 MkII  #1776 M35BC ---

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WindEnsemble
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[quote=HowLin]I assume that it will also direct replace on an M35B also?...[/quote]

No idea. Hopefully, someone else with direct knowledge will reply.

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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WindEnsemble
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Posts: 94

UPDATE! It turns out the alignment is not exact. I will have to make some modifications to my set up. Unfortunately, the upgraded alternator bracket has no means for adjusting in/out (as the one in MaineSail's article does), so I will have to think how to adjust, but I don't anticipate a huge problem. The pulley on the alternator is a little out from the other 2 pulleys.

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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HowLin
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I believe there was an article I read somewhere that indicated a shim was placed between the bracket and the block?  Searched it out on this site...  ​https://www.catalina36.org/forum/technical-discussion/retro-alternator-b...
Don't know if this applies in your case?

---- Howard & Linda Matwick ----

--- S/V "Silhouette" - Nanaimo, BC ----

--- 1999  C36 MkII  #1776 M35BC ---

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[quote=HowLin]I believe there was an article I read somewhere that indicated a shim was placed between the bracket and the block?  Searched it out on this site...  ​https://www.catalina36.org/forum/technical-discussion/retro-alternator-b...
Don't know if this applies in your case?[/quote]

Thanks, HowLin. My problem is that my bracket is already as aft as it can go, but the pulley is still a little too far forward. If I understand correctly, the M25XP came with this bracket. Maybe the new one at Catalina Direct will work better? Ideally, it would be adjustable forward and aft so I could install the new 90 amp alternator and still be able to use the 51amp for a backup, adjusting the bracket as necessary.

S/V Wind Ensemble
1987 C-36 Wing Keel
Universal M25XP 23hp
Hull #705
Coastal Alabama

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Backwater
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Seven years on and I'm about to follow in your footsteps - replacing an externally excited Mando 51A alternator with a Leece-Neville 90A. Your comments and fault-finding have been very helpful - just want to say thanks. I'm fitting  it to a Universal M35B and have ordered two pulleys in order to increase my chances of alignment success. All the best, Craig

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Haro
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Regarding the grounding to the engine block: I learned the hard way after replacing the alternator bracket that the new bracket was painted everywhere including inside of the bolt holes. This provided unreliable ground connection, so the alternator failed next. I add a #8 ground wire to the alternator ground lug. No more problems.
I suspect your new alternator was also painted on all surfaces so the retaining bolt would not provide ground. By providing a grounding cable to the shunt ( opposite side from battery) you can avoid problems.

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Backwater
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I'm having trouble with the new alternator. The field winding seems to not be working despite flashing it. The wiring is pretty simple, or perhaps I'm the one who's simple!

1. Connected +ve terminal to the batteries

2. Connected a separate line from the -ve terminal to the engine block. 

 

There is a good battery voltage across the +ve and -ve as you would expect.

 

Connected one AC terminal to the tachometer.

 

No output when the engine is run. Tried ‘flashing’ the field coil by a. disconnecting the regulator from the ac terminal to avoid damaging the regulator. b. Applying a 12v jumper wire to one AC terminal and ground to the other AC terminal for a second or two. Reconnected the regulator. Ran the engine, still no output.

It's a Leece Neville 90A.

I've written to ASE to see if they have any information that could help. Meanwhile I hope there is someone on this forum that could help.
Thanks,

Craig
SV Wanderlust
Hull 2060
Dubai, UAE

Really could use some expert advice as alternators clearly are not my strong suit!

As an aside, the alignment of the alternator pulley is out by about 5mm (forward). Not much I can do fore/aft on the M35B unless I grind down the back of the alternator mount and insert a washer of the same width at the front. Trying having the pulley machined to bring it aft by about 4mm which won't be perfect. Sigh.

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Backwater
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I thought it worth sharing my experience for the benefit of anyone else trying this mod. Further to my last, I removed the new alternator and bench tested it. It worked. Not sure why it didn't work after the first installation but maybe my flashing wasn't effective for some reason. Anyway now have a fully functioning alternator. I had a new pulley fabricated to fix the alignment issue and to match the 2" internal diameter of the old pulley so the RPM wouldn't need recalibrating and so I could use my existing stock of v-belts!. Smaller internal diameter pulleys rendered my v-belts obsolete as they were too long - I could tension the belt but with no room to adjust outwards as the belt stretched.
The only noticeable outcome of the above mods is the RPM doesn't indicate until I advance the throttle slightly. I guess this relates to the self-excitation of the alternator. If I then back the revs back to idle it keeps working. Ultimately I will change the pulley again to a smaller internal diameter with a shorter v-Belt which should solve that minor issue.
Hope this helps someone in the future.
All the best,
Craig
 

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