20 pole Tachometer

[The Force power]

My Bayliner Capri did not come with a Tachometer & I'm thinking to install one.
I've all of the old post regarding the 20 pole that I require (90 hp Prestolite ignition)
I also read that they are getting harder to obtain by the years, but I found one (not exactly what I wanted)

I'm pretty sure this is a 20 pole, please confirm

 

[The Force power]

Okay, point taken

 

[roscoe]

Really don't know what you have in the photo.

Looks like Sierra started making some 20 pole tachs again.
Sierra International 69044P 0-7000 RPM Dial Range Amega Domed Electric Tachometer for Force Engines, 3"

Does not mention 20 pole in the ad, but
Just read a review from a guy that used one on his Force 125.

sierra's Tech support at 1-877-663-8396

$80 on A m a z o n

 

[The Force power]

yup found it also on other sites with it mentioned;
Designed to operate only on 12 volt Chrysler and Force outboard engines with a 20 pole alternator or stator. [h=1]Sierra Marine Amega Series Tachometers 69044P[/h]

 

[sam am I]

Thinking because that thing says "4 cylinder only" and doesn't have a "poles" setting(I can't see any), the tach is expecting to see 2 pulses/rev. Typically this would be a 4 cylinder 4 stroke (or a 4 pole stator or alt).

So, if I'm guessing right here

20 poles = 10p/r (pulses/rev)

(10p/r)/(2p/r) = 5

If I'm right and you hook that thing up to a 20 pole stator/alt (10 p/r sig. source) and the engine is idling around for example 800 rpm, the tach should read 800*5 or around 4500RPM.

I say this because a 4 or 6 or 8 cylinder engine can all have a alt/stator running 20 pole windings, right? Perhaps each having different current ratings and the like but, still can all have the same pole #'s, right?

Therefor, stamping "4 cylinder only" wouldn't make sense stamped on a tach that can run on any of those cylinder engines(4/6/8) because all, as we[me] just established, can all be running the same pole # stator/alt.....It then must be intended for as I listed above, expecting 2 pulses/rev NOT 10 pulses/rev (20 poles).:facepalm:



https://forums.iboats.com/forum/boat...4696-tach-test

 

[The Force power]

Thank you Sam for the lesson, you made me aware of what to look for.
This gauge was used on a 4 Cyl./ 2-stroke Force (prestolite ignition)

Quote;I say this because a 4 or 6 or 8 cylinder engine can all have a alt/stator running 20 pole windings, right? Perhaps each having different current ratings and the like but, still can all have the same pole #'s, right? {quote**

with that in mind, this will not work on a 3 Cylinder/ 20 pole stator, but it only gets one signal of one winding so How would it know 3 or 4 Cyl. ??:noidea:

 

[racerone]

??----Many tachometers run of the alternator signal / output.------Has nothing to do with 4 stroke / 2 stroke or the number of cylinders.

 

[The Force power]

??----Many tachometers run of the alternator signal / output.------Has nothing to do with 4 stroke / 2 stroke or the number of cylinders.

Good morning racerone,
Okay, with that being said; a 20 pole Tach. would work on a 3 Cyl. & 4 Cyl. ? (providing the right stator for a 20 pole)

if it would, it would confirm my theory

 

[racerone]

???-----Is Post #7 not clear ?---Or am I missing something ?

 

[GA_Boater]

Racer - The force ain't with you. LOL

(providing the right stator for a 20 pole)

if it would, it would confirm my theory

What theory? You can't confirm a theory based on faulty knowledge. How can you have a wrong 20 pole stator?

And the number of spark plugs has nothing to do with stators.

 

[The Force power]

Racer - The force ain't with you. LOL



What theory? You can't confirm a theory based on faulty knowledge. How can you have a wrong 20 pole stator?

And the number of spark plugs has nothing to do with stators.

NICE!! I did not expect this from a "Moderator"
If..you would of taken the time to look at the first post/picture you may have under stood what I was asking

but I have my answer now, thank you all for the efforts

 

[The Force power]

???-----Is Post #7 not clear ?---Or am I missing something ?

Nope you did not miss anything, it took me a second to understand what you were "saying"

thank you

 

[GA_Boater]

NICE!! I did not expect this from a "Moderator"
If..you would of taken the time to look at the first post/picture you may have under stood what I was asking

but I have my answer now, thank you all for the efforts

I did look at the pic/post. How can you be helped if questions are not asked and misconceptions aren't put to rest?

Glad you have your answer.