How many poles

Poly · 02 January 2008, 09:57

No not another political ribnet thread...

...I am planning to fit a tacho to my boat. To do this I need to know how many poles the alternator has - is there an easy way to find this out - I can't find it in the Manual.

Engine is a 20 HP 2-stroke Yamaha, 2 cylinders. It has electric start with battery connections. I believe the model number is 20D.

Locozodiac · 02 January 2008, 15:30

Hola Polwart

There are some engines in which you cannot put a tach because there is no wire harness available, one nice alternative that was using on a Evinrude 2 stroke 15 HP is the Tiny Tach from Kohler Engines, is an induction hour/tach meter, don't need a dedicated wire harness for it or guessing/messing/experimenting with other cables until you find the right ones.

When the engine is running shows the engine rpm's on a digital display, when engine shut off shows the working hours, very nice for scheduled maintenances. Just 2 wires, the red wrapped 4 turns on any wire plug, the black to any ground. If possible to find locally, specify the engine stroke.

Used to have it installed on the engine exterior cowl in front of the acelerator arm, now sits peacefully inside a Tohatsu 2 strokes 18 HP engine. One nice thing about tachs is that you can WOT your boat/engine very precise for max speed and performance.

See attached photo as a instalation refference, happy boating

Locozodiac

bedajim · 02 January 2008, 15:45

Quote:

Originally Posted by Locozodiac

Hola Polwart

There are some engines in which you cannot put a tach because there is no wire harness available, one nice alternative that was using on a Evinrude 2 stroke 15 HP is the Tiny Tach from Kohler Engines, is an induction hour/tach meter, don't need a dedicated wire harness for it or guessing/messing/experimenting with other cables until you find the right ones.

When the engine is running shows the engine rpm's on a digital display, when engine shut off shows the working hours, very nice for scheduled maintenances. Just 2 wires, the red wrapped 4 turns on any wire plug, the black to any ground. If possible to find locally, specify the engine stroke.

Used to have it installed on the engine exterior cowl in front of the acelerator arm, now sits peacefully inside a Tohatsu 2 strokes 18 HP engine. One nice thing about tachs is that you can WOT your boat/engine very precise for max speed and performance.

See attached photo as a instalation refference, happy boating

Locozodiac

I like that

Googled a uk supplier too

http://www.tinytach.com/tinytach/canadian.php

Poly · 02 January 2008, 16:17

Loco - thanks - I saw that on ebay a little while ago and did consider it. But I do have the wiring harness for the tacho and so I would like to make use of that directly. I have spotted a "universal" teleflex dashmount tacho which will do the job and is a reasonable price - all I need then is to know how many poles - so I can set the switch on the back. If I can't get it then trial and error will probably prevail - but then whenever it gives an odd reading I will doubt the set up...

Nos4r2 · 02 January 2008, 17:32

Can't tell you how many poles you've got but I can tell you how to get the rpm correct....

Take a timing strobe with an RPM meter and attach it to your engine.

Set the tacho up to show the same number of RPM.

Dirk Diggler · 02 January 2008, 17:51

All the outboards I've ever fitted have been 12 pole, although they have been larger capacity/horsepower to the model you have.

Poly · 02 January 2008, 18:28

Quote:

Originally Posted by Dirk Diggler

All the outboards I've ever fitted have been 12 pole, although they have been larger capacity/horsepower to the model you have.

Thanks dirk. According to the manual for the tacho, most of the 4 strokes >25 HP are 12 pole. But the 2 strokes less than about 90 HP are a right jumble. Yamaha 2 strokes in the 9.9-15 HP range are listed as 4 pole and 25-70 HP are listed as 6 pole. Unfortunately they don't list the 20! So presumably it is will be one of those?

David G · 02 January 2008, 18:50

Quote:

Originally Posted by Polwart

Thanks dirk. According to the manual for the tacho, most of the 4 strokes >25 HP are 12 pole. But the 2 strokes less than about 90 HP are a right jumble. Yamaha 2 strokes in the 9.9-15 HP range are listed as 4 pole and 25-70 HP are listed as 6 pole. Unfortunately they don't list the 20! So presumably it is will be one of those?

This document implies that it is a 4 pole due to it stating Yamaha 6HP-25HP:

http://faria-instruments.com/site_manuals/IS0012u.pdf

Orve

Poly · 02 January 2008, 19:06

thanks - but only until 1987 - or am I misreading that? i think the problem is they don't seem to have sold the 20 HP in the US therefore its not listed.

David G · 02 January 2008, 19:35

Quote:

Originally Posted by Polwart

thanks - but only until 1987 - or am I misreading that? i think the problem is they don't seem to have sold the 20 HP in the US therefore its not listed.

What year is it then?

jwalker · 02 January 2008, 19:35

Stick a meter on the output leads and turn the engine by hand, see how many bumps you get in one turn. Or, take the flywheel off and count em. Or, set the tacho by gestimate and see what revs it reads at tickover. Your engine likely ticks over at about 1000rpm. Adjust tach as necessary.

Poly · 02 January 2008, 20:02

Quote:

Originally Posted by Orville

What year is it then?

2005 (I believe they started making them in 2001).

Quote:

Originally Posted by Nos

Take a timing strobe with an RPM meter and attach it to your engine.

I don't have one. Although I can probably borrow one when I go up to fit it to the boat. I was hoping some guru here would have just known the answer...

Quote:

Originally Posted by JW

Stick a meter on the output leads and turn the engine by hand, see how many bumps you get in one turn. Or, take the flywheel off and count em. Or, set the tacho by gestimate and see what revs it reads at tickover. Your engine likely ticks over at about 1000rpm. Adjust tach as necessary.

Thanks Jeff - guessing would have been my fall back poistion (since it is almost certainly 4 or 6) - but if tickover was 800-1200 RPM it wouldn't be clear which setting was right. I wasn't sure how easy it would be to get to the relevant parts to count it - you make it sound easy. Are you suggesting that I will see a measurable voltage spike (DC) (on my £10 maplin digital multimeter) at the tacho input each time the flywheel passes a pole?

thanks everyone.

David G · 02 January 2008, 20:17

anything of any use here?:

http://www.boats.net/parts/search/Ya...005/index.html

jwalker · 02 January 2008, 22:26

Quote:

Originally Posted by Polwart

Thanks Jeff - guessing would have been my fall back poistion (since it is almost certainly 4 or 6) - but if tickover was 800-1200 RPM it wouldn't be clear which setting was right.

Yep that would be the tricky one but listening to 800 would sound kinda slow. If you had that unclear situation, you could back off the revs a few hundred. I doubt whether the engine would run steadily at 400rpm but it would probably bark along at 800.

Quote:

Are you suggesting that I will see a measurable voltage spike (DC) (on my £10 maplin digital multimeter) at the tacho input each time the flywheel passes a pole?

I think you'll get a twitch if the flywheel is moving at a reasonable speed but digital meters are not so good. You might get the pulse when the meter isn't looking. At a push, you could try and put a led across the output. I'd stick a 100ohms or so in series to give it a bit of protection. They fire up at about 2v so you might get a flash. Put a dot of tipex on the flywheel so you can find a pole and then move back to find the next. Once you've got two adjacent poles you should be able to deduce the number by the angle between the ones you've found.

Nos4r2 · 02 January 2008, 23:08

Does this look familiar?

It appears the same as this 25hp bar the power output. Same bore/stroke/cc/alt output/ and same weight to within half a kilo.

Poly · 03 January 2008, 10:28

Quote:

Originally Posted by Nos4r2

Does this look familiar?

It appears the same as this 25hp bar the power output. Same bore/stroke/cc/alt output/ and same weight to within half a kilo.

Nos - thats the one. With an "identical" spec - I assume the "altenator" is going to be the same. I'll start with that assumption (6 pole) and then resort to more scientific approach if the results look suspect based on Jeff's magic calibration by ear trick of if it sounding fast/slow!

9D280 · 04 January 2008, 11:46

Polwart,

Funnily enough I'm about to try connecting an old Suzi tacho to my Yam..... Found this, as I am also missing any useful tech info.

http://www.downloadingfiles.co.uk/te...0Reference.pdf

Page 15.

Worst case, connect it up, set it to "12 pole". If you get an idle speed of 3-400-ish rpm, notch it back to the "6- pole" seting!

Poly · 04 January 2008, 13:22

Quote:

Originally Posted by 9D280

Polwart,

Funnily enough I'm about to try connecting an old Suzi tacho to my Yam..... Found this, as I am also missing any useful tech info.

http://www.downloadingfiles.co.uk/te...0Reference.pdf

Page 15.

Worst case, connect it up, set it to "12 pole". If you get an idle speed of 3-400-ish rpm, notch it back to the "6- pole" seting!

thanks