Tach for '73 Chrysler 55 HP - How many poles?

[touvell]

I'm trying to figure out what tach setting I need for my 1973 Chrysler 55 HP outboard. It's the alternator model with battery ignition.

It does _not_ have the Prestolite ignition that Chrysler/Force used in later years.

I pulled the flywheel and there are 8 magnets in it. The stator is a Wico stator with 24 coils on it. I found a picture of a prestolite stator, and counted 20 coils on it, so does that mean I have a "24-pole" alternator. I've never seen a 24-pole tach.

I've read in various places that the number of poles is the number of magnets, and I've read that the number of poles is the number of magnets X 2, and I've read that the number of poles is the number of coils on the stator, and I've read that the number of poles is the number of coils on the stator X 2.

So, what do I need? Is the number of poles tied to the number of magnets, number of stator coils, or some combination of both? There's a lot of conflicting and confusing information out there, can you guys clear this up for me?

BTW, I've looked at tiny tachs, but would rather have the analog tach mounted in the dash. Surely there's one that will work. I can get a 4-10-12-20 pole, or a 4-6-8-12 pole for less than the cost of a tiny tach.

Thanks a lot,

Dave

 

[eurolarva]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Contact the marine doctor. He should be able to help you

http://www.themarinedoctor.com/cgi-bin/YaBB.pl/YaBB.pl

 

[touvell]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Thanks eurolarva,

I browsed through the forum over at TMD, and left a message there.

Dave

 

[ricksrster]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Accordig to the Teleflex data, you have a 20 Pole alternator. They make a tach for 20Pole Chrysler/Force motors. The part number is 53743P. Installation instructions are here: http://ww2.tflx.com/PDF/99272.pdf

 

[touvell]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Rick,

Thanks for the info, but a couple of Chrysler "old-timers" have told me that Teleflex is a little off on their data. The 20-pole alternator was the Prestolite" alternator, which wasn't used on Chrysler motors until sometime around 1980 or so. That's why I pulled the flywheel to count the magnets and stator coils. The problem is, once I counted them, I didn't know how to "interperet the data."

The Marine Doctor that eurolarva referred me to said that he's always used the number of stator poles divided two, which in my case would be a 12-pole alternator.

I'm going to try that and see if it works. I tried the 20-pole setting and it seemed to be reading way too low.

I'll update the group when I have this all figured out.

Dave

 

[roscoe]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Number of magnets on the flywheel, times 2 = # of poles.

(each magnet has 2 poles, a north and a south pole)

 

[touvell]

Re: Tach for '73 Chrysler 55 HP - How many poles?

roscoe,

I've seen that formula before, too. The problem is that I have 8 evenly-spaced magnets, which would be 16 poles using the magnets X 2 method. I've only seen tachs for 4, 6, 8, 10, 12, and 20 pole alternators. So does that mean that there isn't an alternator-driven tach that will work with the old Chryslers that were made before they started using the 20-pole Prestolite alternators?

Before this is over I may end up begging, borrowing, or even buying a photo- or contact-tach just to see what's truly right.

Thanks,

Dave

 

[roscoe]

Re: Tach for '73 Chrysler 55 HP - How many poles?

Hmmmm?

Well, for what its worth, Chrysler 55 and 65 hp were supposed to have 20 tachs, according to the chart HERE:
http://ww2.tflx.com/PDF/99320.pdf

OK, been reading a little.
If your motor has the MAGNAPOWER ignition, you will probably not find a tach that will work with it.