Alternator help

[Pete the Cat]

I have a defective old Motorola 12N-51A-8428 alternator on the 25XP on my 32-200. I am not interested in doing a major external regulator and huge upgrade that Maine sail shows on his site (I urge folks to send him a donation--he had a stroke and is partially paralyzed and needs the money)---I have been there done that on my Tartan electrical system for longer cruises because I have refrigeration and a lot of stuff there for extended cruising. I mostly use my Ericson 32-200 for overnight and coastal cruises and have a couple of 120 Ah batteries that seem to supply things fine. I do not want complication. I am looking for as close to a drop in replacement as possible with a possible upgrade in Ah output to maybe 70 or possibly 105 (can you drive that with that measly 3/8" belt?). I think I have found the problem and can eventually fix the old alternator, but would like a new replacement. Catalina Direct seems to offer something, but it is not really drop in as it seems to have no sensing and no tie to the tach. Anyone have a suggestion?

 

[Loren Beach]

On our OEM Universal M25XP, we never seemed to run short of charging with the stock Moto 50 (or about that size) alternator. I had it rebuilt once at somewhere over 1000 hours. The shop that did the work does a lot of marine alternators where they change the internal to external regulation, as well. "Choices and options'.
Our house bank is two Trojan T-145+ batteries, and we run the fridge all the time.
... just a little data point... maybe you just need to have it refurbished so it puts out the rated amps again, perhaps? Unless you have more power needs and spend lots of time at anchor.

 

[Pete the Cat]

On our OEM Universal M25XP, we never seemed to run short of charging with the stock Moto 50 (or about that size) alternator. I had it rebuilt once at somewhere over 1000 hours. The shop that did the work does a lot of marine alternators where they change the internal to external regulation, as well. "Choices and options'.
Our house bank is two Trojan T-145+ batteries, and we run the fridge all the time.
... just a little data point... maybe you just need to have it refurbished so it puts out the rated amps again, perhaps? Unless you have more power needs and spend lots of time at anchor.

I agree with your assessment and recommendation. I have a hopped up externally regulated alternator on my Tartan 37 and 440 ah of golf cart batteries--all left over from my international cruising days--and it was really overkill capacity, even back then, despite my need for refrigeration in the tropics and passage days without recharging. I have since become dedicated to the "less is more" philosophy and equipping to my actual usage--coastal and weekend trips. I am rebuilding my old Motorola alternator (still trying to find a replacement internal regulator for it though). I am really looking to put something new that I can still easily buy parts for in its place and keep the old one as a spare. Would really like to find something that is drop in simple and will fit without a lot of rewiring and something that will communicate with the tach and sense the system need like the old one. Catalina Direct has a Leece Neville that they say is drop in for the 25XP, but I do not see a tach tap or remote voltage sensing of the old Motorola and it is a 105 A which is more than I need and seems to be a bit of a load for the puny 3/8" V belt. I believe the Kubota blocks for all these marinized engines were originally designed for small tractors and forklifts that used 35A alternators. Not sure it is a great idea to put a huge alternator on the pump and crank bearings anyway. The shop I took it to really gave up when parts were not available.
Thanks for your input.

 

[G Kiba]

Ray,
Last week I thought my alternator (12N-51A-8428 Universal M18) had a bad bushing and was and on it's last legs. I freak out and tried to get a replacement on order because I didn't want to miss the Three Bridge Fiasco, a group sail to Benicia, and the last Berkeley mid-Winter race. All in the next three weekends

The alternator upgrade replacement at Catalina Direct is back ordered 8 weeks! I ended up ordering this alternator on Amazon. It just came in yesterday and it has both the tach and voltage sense connections. It also looks of good quality. My current alternator, (also a Leece Neville) does not have the voltage sensing?

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwie2aSUo831AhXVPn0KHXFvDs4QFnoECD8QAQ&url=https%3A%2F%2Fwww.amazon.com%2FRareelectrical-ALTERNATOR-COMPATIBLE-UNIVERSAL-8EM2004KBS%2Fdp%2FB07TVYM13W&usg=AOvVaw3BCYrBzG2Cz8oJaa4OQrLK

Anyways, it turned out not to be the alternator so I am keeping it as a backup. My push-button starter button sometimes sticks leaving the starter on while the motor is running. Sounds like a bad bushing in the alternator because the starter is right behind the alternator. Watch out for the cheep buttons. It's had to tell if the button is stuck in the on position through the thick rubber cover.

 

[Pete the Cat]

Thanks for your note. My problem turned out not to be the alternator after taking mine to the shop to have it rebuilt (and uneeded parts on order). But there is nothing wrong with it. I have two copies of Nigel Calder's Boat Maintenance book but confess that I thought I knew most of the stuff in there from rebuilding boat systems for the last 45 years--I was wrong. I decided that maybe I should review Calder's trouble shooting guide and use it on my alternator just to make sure I did not overlook something. He starts out where you should: with the simplest, most basic reason an alternator might not work well: Are the connections from alternator to the battery clean and without resistance? I put a VOM on the + side and things were fine. I checked out the neg ground (engine block to battery) and guess what? Much resistance. I had rewired a lot of this boat over the last year, but never bothered with this most fundamental and important connection because it looked fine physically from above and was hard to access back on the bell housing. This boat had been sailed very little when I bought it a year ago and the bolt connecting the battery negative to the block had the Universal chipped brown paint on the top and appeared to be secure. HOWEVER, the bolt securing the battery cable was just stuck in the hole and, because it was a collared bolt that was too long, could not have EVER been tightened adequately to make a decent connection to the battery. I surmise the boat has been in this condition since it was built. Someone stuck a too long bolt slapped a nut on it and just left it hanging there--let the owner sort it out. This explains a lot of problems I have been having. It usually started well, but occasionally it would not-so I kept replacing connectors and lengths of wiring---and I had replaced the trailer connector and most of the starter and alternator wiring in an attempt to chase the problem. Sometimes the oil pressure light (I added a buzzer) would work and sometimes not. Now everything appears to work. Not sure what the moral of this story is. Has to do with being arrogant after all these years and forgetting to respect Occam's Razor in trouble shooting.
FWIW.

 

[jtsai]

Glad you found the source of the problem. My problem solving logics are often clouded by overwhelming amount of divergent information available. My 25XP intermittent engine starting problem was attributed to an aging tubular fuse with weak springs, that is after replaced batteries and glow plugs.

 

[Loren Beach]

It's Great to find and fix a problem. The longer I live, the more respect I have for Mr Occam... !

 

[G Kiba]

Glad it was not the alternator and only a ground issue! I had my alternator tested by a small shop "Alternators Unlimited" in Berkeley. And it passed! The owner tested it for free while I waited. Great place. Glad to see small shops like it still exist.

Owning a previously owned boat often requires good detective skills to keep it running well. I changed out the secondary filter and found that it was rusted in-place and still had the Universal copper colored paint? I wonder if it was ever changed? Or maybe someone replaced the motor some years back and neglected to change the filter? I have no idea? However, the 2 micron Racor primary filter (also came with the boat) must be working well?

 

[Pete the Cat]

Glad it was not the alternator and only a ground issue! I had my alternator tested by a small shop "Alternators Unlimited" in Berkeley. And it passed! The owner tested it for free while I waited. Great place. Glad to see small shops like it still exist.

Owning a previously owned boat often requires good detective skills to keep it running well. I changed out the secondary filter and found that it was rusted in-place and still had the Universal copper colored paint? I wonder if it was ever changed? Or maybe someone replaced the motor some years back and neglected to change the filter? I have no idea? However, the 2 micron Racor primary filter (also came with the boat) must be working well?

Thanks for the heads up on the Berkeley place. The ACS rebuilding place in Oakland does not have that kind of old expert there (they test rectifiers and voltage but really do not seem to be able to check amp load) and--as you say--they are getting harder find. I have worked on previously boats over the years and rebuilt four of them from the ground up and agree--you learn a lot about previous owners from their boats. Most seem to work on doodads, electronics and putting in sophisticated systems (often with nightmarish techniques) rather than real basic maintenance. I think a lot of folks change their primary filters when they have a problem and the engine will work again, but assume that the secondary is forever. I would say someone put that 2micron on there, as most of the engine manufacturers recommend a 10 or 20 for a primary and the secondary is usually 2micron. Some folks think "more filtration is better", but my mechanic friends say that it needlessly strains fuel pumps and injector pumps to put that much load on the engine's effort to draw fuel. FWIW.