Alternator Recomendations for 25XPB

[jimmcgee]

Over the weekend I noticed that my tach was reading high. About 500 RPM above normal at idle, 1,000 RPM above normal at 2,000 RPM etc. to a reading of approx. 4,000 RPM at full throttle.

I didn't get a chance to check its output, but since the tach is fed off the AC tap on the alternator my guess is the alternator is shot.

Any recommendations for replacment alternators, pros/cons. Right now I have the stock two battery setup, but have kicked around the idea of a second house battery.

Opinions?

Jim

 

[fortitude]

Jim, just replaced mine this past weekend. Leece Neville, 90 amp. Model # 8MR2069TA. In my case it was a direct bolt on replacement, no modifications required. You'll have the option to use the internal regulator already installed or opt for an external smart regulator. Check the catalina 34 forum for tips and advice, that's how I made my choice. $246.00 w/ new pulley.
Bill

 

[fortitude]

P.S.
Jim, this installed on a m25XP.

 

[Stu Jackson]

Jim, Bill's right. Don't waste your hard earned $$ on a Balmar. Here's the link Bill was referring to:

Woops! Sorry our C34 'site is down for a few hours for maintenance.

Try this: Google "Maine Sail Leece Neville" or do a search upper right blue tab right here. It should link to Maine Sail's own write-ups on why Leece Neville is the best bang for your buck. I spoke to the Washington State rep a few months ago and he's great to deal with. Name is Bob.

When our website's up again, I'll post the link, unless you've found it already.

What engine? External or internal regulation?

Many of us have "been there done that" and can help.

 

[Stu Jackson]

Try these - Leece Neville

Converting a Leece Neville Alternator to External Regulation by Maine Sail
http://c34.org/bbs/index.php/topic,4879.0.html

Alternator Sources by Maine Sail (Reply #16)
http://c34.org/bbs/index.php/topic,5686.15.html

 

[degreeoff]

Hi guys, look I don't know much......I did however just measure the width of the ear on the alt and call dynathrust in Baltimore for a replacement. For the cost of the R.N I got a 90 amp car alt and a Pulley and a external zantrex regulator.....it just needs to fit, an alt is an alt!

 

[jimmcgee]

Stu, thanks for a couple of VERY good links on the subject.

I need to spend some time reading...

 

[jimmcgee]

BTW, I'm assuming that what I'm seeing means a bum diode so the alternator's not charging the batteries when motoring.

Any danger running this way through the end of the season -- mid-November if the weather holds?

I'd rather add this to my winter project list and do it after haul out and not lose any of these last few sailing days.

 

[Stu Jackson]

Any danger running this way through the end of the season -- mid-November if the weather holds?

Shouldn't be.

How Alternators & Regulators Work (by Maine Sail): http://forums.sbo.sailboatowners.com/showthread.php?t=125392

 

[Maine Sail]

Over the weekend I noticed that my tach was reading high. About 500 RPM above normal at idle, 1,000 RPM above normal at 2,000 RPM etc. to a reading of approx. 4,000 RPM at full throttle.

I didn't get a chance to check its output, but since the tach is fed off the AC tap on the alternator my guess is the alternator is shot.

Any recommendations for replacment alternators, pros/cons. Right now I have the stock two battery setup, but have kicked around the idea of a second house battery.

Opinions?

Jim

Jim,

Don't jump to conclusions to early. You need to test the output of the alt by measuring across the B+/output stud and neg/alt case/eng block with a DVM.

If the voltage is higher than the battery resting voltage, with the motor off, the alt is working. Stator outputs are pretty darn reliable compared to tachs and the tach wiring. Start with the wiring between the tack and alternator AFTER you've determined if the alt is operational.

 

[Bob S]

I was curious why you'd think the alternator is shot because of the faulty tac reading. I'm not a good source for advise but there have been many threads on adjusting the tac. I would thoroughly clean the leads on the back of the alternator first before replacing and use a dvm to check the output as Maine suggests.

Maine, not easy lining up that alternator pulley. Looks like the shaft might be bent, there's a bit of a wobble

 

[Maine Sail]

Maine, not easy lining up that alternator pulley. Looks like the shaft might be bent, there's a bit of a wobble

That was with the OLD BRACKET that should have been upgraded when the first one failed and took out the timing gear case.

It was upgraded shortly after I made that video. This was taken midway through the upgrade.:

 

[jimmcgee]

I was curious why you'd think the alternator is shot because of the faulty tac reading. I'm not a good source for advise but there have been many threads on adjusting the tac. I would thoroughly clean the leads on the back of the alternator first before replacing and use a dvm to check the output as Maine suggests.

Bob,
I know the tachs are not 100% accurate on diesels and sometimes need to be calibrated. But this wasn't a case of the tach reading drifting over time. It was a sudden change when we picked her up off a mooring after lunch, which is why I suspected the failure of one of the diodes in the alternator.

Mainesail brings up a good point and I'll do a quick voltage check. Another culprit could be noise in the tach wiring and the tach is seeing the noise as RPM's. But I haven't made any recent changes or upgrades to systems or wiring.

I thought about corrosion on the terminals. In fact an R&R and repaint of the engine control panel is on the winter to-do list. But I suspect that increased resistance at the connections would lead to a lower tach reading rather than a higher reading as you're attenuating the AC pulses reaching the tach.

I haven't ruled out a bad tach either. It is 17 years old.

As I said in my original post I haven't really had a chance to dig into troubleshooting yet and am looking for ideas since there really isn't much info in the Univeral manuals. It helps to talk things through and generally someone on this forum has experienced the problem you're having

All that said, my inclination is to figure it out, order the parts and deal with it after haul out so I can squeeze out as many days on the water as possible between now and mid-November.

Jim

 

[jimmcgee]

That was with the OLD BRACKET that should have been upgraded when the first one failed and took out the timing gear case.

It was upgraded shortly after I made that video. This was taken midway through the upgrade.:

Maine Sail,
I have the old bracket shown in the video. Can you post where you got the bracket shown in the photo. It looks a LOT more substantial. If I end up doing the alternator I'll do the bracket as well.

Thanks,
Jim

 

[Stu Jackson]

There are a couple of references to it here, with sources: http://c34.org/bbs/index.php/topic,5078.0.html

 

[jimmcgee]

There are a couple of references to it here, with sources: http://c34.org/bbs/index.php/topic,5078.0.html

Thanks Stu !

Ya gotta love this forum. :dance:

 

[Bob S]

Jim,
I agree, you gotta love this forum!
I'd do a double check on the alternator bracket. The MKIII should have the bracket upgrade already.
BTW, I followed Maine's post on the Leece Neville 90A Alternator wired for an external regulator. His pictorial guides are the best I've seen.

 

[Tom J]

Over the weekend I noticed that my tach was reading high. About 500 RPM above normal at idle, 1,000 RPM above normal at 2,000 RPM etc. to a reading of approx. 4,000 RPM at full throttle.

I didn't get a chance to check its output, but since the tach is fed off the AC tap on the alternator my guess is the alternator is shot.

Any recommendations for replacment alternators, pros/cons. Right now I have the stock two battery setup, but have kicked around the idea of a second house battery.

Opinions?

Jim

I had the same problem on my M25-xpb and I was able to remedy the problem by moving the calibration screw back and forth and leaving it in its original position.

 

[jimmcgee]

I had the same problem on my M25-xpb and I was able to remedy the problem by moving the calibration screw back and forth and leaving it in its original position.

Tom, this is a screw on the back of the tach?

 

[Maine Sail]

Tom, this is a screw on the back of the tach?

Yes usually a very small hole with a small Allen head screw. I would not touch this without a digital photo tach in hand to calibrate it against.. These are VERY, VERY sensitive and even just touching it with the Allen wrench can change the display by a few hundred RPM.

When you have a digital photo tach move it back and forth a few times to clean the contacts, then adjust it. You'll then want to check it against the photo tach, at differing RPM, and make a deviation card "while your in there".....