tachometer replacement & alternator magnetic poles

miquelkumar · Post by **miquelkumar** » Jan 8th, '12, 16:08

I have a Universal M-18 on my '84 CD 28 and installing a new tachometer gauge which requires the number of magnetic poles in the alternator in order to calibrate the new tach.. Anyone gone through this exercise that can help?

Thanks,
Mike
619.507.4119

Steve Laume · Post by **Steve Laume** » Jan 8th, '12, 18:34

I did mine a couple of years ago. I forget whether it was four or eight, or whet ever. I have a Baldor alternator so it might not be the same anyway. I do know that went I first put it in, it was reading wrong. I reached in back with a little screwdriver and turned the screw until it read right.

Mine has not be calibrated but at least it is very close and reads consistently, I adjust my RPMs accordingly, Steve.

Maine Sail · Post by **Maine Sail** » Jan 8th, '12, 19:35

Mike,

I am going to guess your M-18 has the original Motorola alt and if it does it is a 12 pole alt. If you have not yet upgraded the alternator bracket this is a VERY wise move. The original brackets are prone to failing. When they fail they can take out the timing gear case casting and puncture the oil filter at at the same time. With the timing gear case broken this becomes a very expensive repair..

Here's the kit: http://shop.torresen.com/ships_store/in ... sku=256891

miquelkumar · Post by **miquelkumar** » Jan 8th, '12, 21:02

Thanks for the info. I will be checking the alternator tomorrow to determine if it's original or not. I will also look into the upgraded bracket if it has not be changed as well.

Thanks again for the quick reply. Gotta love the CD Forum.
Mike
Joe Toe, CD 28

Steve Laume · Post by **Steve Laume** » Jan 9th, '12, 09:08

What is it, or where does the bracket fail? It must be the pivot bracket if it is able to do damage to the engine.

Nearly $200.00 is a good bit to spend with much of it on parts that do not seem to directly effect the problem. Does the bracket itself fail or is it that the mounting holes on the engine are not adequate? It seems like I could weld up a modification to correct the current bracket.

A picture of the replacement bracket would tell a great deal. I realize this might be very hard to get as the alternator would be in the way.

Thank you for the heads up but now I have one more thing to consider upgrading that will not add much joy. It could prevent a great deal of sorrow though. I will inspect the area and see if I can determine the possible problem area, Steve.

Maine Sail · Post by **Maine Sail** » Jan 9th, '12, 11:56

Steve Laume wrote:What is it, or where does the bracket fail? It must be the pivot bracket if it is able to do damage to the engine.

sometimes the old bracket breaks:

Steve Laume wrote:Nearly $200.00 is a good bit to spend with much of it on parts that do not seem to directly effect the problem.

Actually the upgraded bracket nearly eliminates the problem. It bolts directly to the manifold and is significantly stronger.. I have even seen a failure of the old style bracket with the diminutive 35A Motorola alts so the alt size is not the only contributing factor.

Steve Laume wrote:Does the bracket itself fail or is it that the mounting holes on the engine are not adequate? It seems like I could weld up a modification to correct the current bracket.

Sometimes it is the bracket and sometimes it is the mounting foot on the timing gear casting. If you crack the mounting foot on the timing gear case this becomes a MAJOR expense....

http://forums.catalina.sailboatowners.c ... 1310478756

http://forums.catalina.sailboatowners.c ... 1310478756

Steve Laume wrote:A picture of the replacement bracket would tell a great deal. I realize this might be very hard to get as the alternator would be in the way.

As you can see it mounts directly to the manifold. Be aware that on some engines you'll need to pull the entire manifold off to replace the studs with the longer ones supplied in the kit. This is a good time to check or replace the exhaust manifold and the injection elbow. usually the manifold is fine but you'll need the three new manifold gaskets to put it all back together.

I am actually right smack dab in the middle of this project on an Ericson 32 with an M-25. This is about the 12th one I've done or more.. This owners timing gear case had already been replaced once but his clueless yard slapped the old bracket back on so it could fail again. An $1800.00 bill and still not fixed correctly... Argh....

This was on an M-25XP but the bracket is the same for the M-18, M-25 & M-25XP..

Steve Laume wrote:Thank you for the heads up but now I have one more thing to consider upgrading that will not add much joy. It could prevent a great deal of sorrow though. I will inspect the area and see if I can determine the possible problem area, Steve.

This has been a known problem for a long time so your bracket may have already been changed. If it looks like the one above it has been. If not then you could lose it at any time. I am constantly amazed at how many M series engines I see with a new timing gear case and the old bracket....Doh'.......

miquelkumar · Post by **miquelkumar** » Jan 10th, '12, 01:07

Damn, I dream of that kind of motor access. I do have the Motorola alternator and it looks as though the original mounting bracket.

Thanks for all your help.

BTW, how do you insert images. I clicked on the Img box but didn't get a brower to find my image.

Steve Laume · Post by **Steve Laume** » Jan 10th, '12, 15:16

Now I get it! The old bracket always seemed a bit flexy. The new one makes a great deal of sense. I am sure I could weld something up but given the Cape Dory access to this area and the complexity of the new bracket, the $200.00 is probably well worth the money. I have already done the plumbing modification with the 90* hose routing but I suppose having a spare is not a bad thing either.

I will make one quick check with my local Kabota tractor dealer before I order but it definitely seems like a worthy investment. With the age of our motors and the fact that I upgraded my Alt. I am sure I am living on borrowed time. Having that kind of failure far from home or anywhere for that matter would be a major suck fest.

I just wish I had known about this when I had the engine sitting in my shop two years ago. Thank you so much for bringing this to my attention, Steve.