FS14 Wolf's build

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narfi
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Re: FS14 Wolf's build

Post by narfi » Tue Oct 30, 2018 4:06 pm

Capt UB wrote:
Tue Oct 30, 2018 2:52 pm
The tach it's self can be off by ???
I am so confused. I have never used one of these before, but if it is just a tiny computer counting induction pulses, how can it be off if it is setup properly? It just counts pulses and divides or multiplies those by a number you or the manufacture specify to give you an exact (not approximate) rpms?

I have used spoke counters on a bicycle when I was young (I think it was magnetic) to a digital display.
I worked with magnetic pickups plugged into a magnetos for a digitial display.
I have worked with light reflected on reflective tape for a digital display.
I have worked with a cheaper light reflected that just counts blades and you select 2,3,4 blades to calculate for a digital display.
And of course cables for an analog display.

Other than the cable and analog display, it seems the numbers should be straight forward x/y=z math like this isn't subjective is it?

I've not used a tach like this wraped around the cables, and I like learning things........ So how can x/y not equal z?
Does the weak spark not always register on the device or something? It seems this would give you sporadic readings, not something that was off by x% consistently.....

Your target is 950 and 5000-6000
You read 600 and 3000

https://www.tinytach.com/pdf/Tiny2AInst ... s11263.pdf
You have a steady reading, if it is idling smoothly in what 'feels' like the right range, the instructions tell you how to change the settings till you get the correct reading based on sparks per revolution. (8,6,4,3,2,1,1/2 sparks per revolution) It looks like your currently set at about 1.5x the one it should be set at..... for example if you have it set to 6 sparks per revolution you should change it to 4(from 60 to 90 degrees), if you have it set to 3 you should change it to 2.(from 120 to 180 degrees)
With those new settings you would end up with 900 and 4500 rpms and could then start making your adjustments.

Googling around find lots of interesting and conflicting information but people struggling.... so you certainly arent alone..... :P

Edit: the more I read the more I think you want to wrap around just one cable and select 2 sparks per revolution, if that cable doesnt work then try the other cable, some people reported that working for them.



Jaysen
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Re: FS14 Wolf's build

Post by Jaysen » Tue Oct 30, 2018 4:36 pm

Well, induction is a funny thing. The number of wraps will change the sensitivity to the actual spark. Also, more wraps actually store some charge impacting the sensitivity further. Additionally the velocity of the magnet in the flywheel as it passes the inductor coil will impact exactly how much the ignition coil can output. So...

The EE in me says that you actually want FEWER wraps in the spark wires to DECREASE sensitivity and allow more discrete sensing of each pulse. That should allow you to detect the two weak pulses on the exhaust cycle.

So try two wraps on both wires and run the motor in a tub to see if the rpm at idle gone up into “the right zone”.

Just an idea.
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Re: FS14 Wolf's build

Post by Capt UB » Tue Oct 30, 2018 4:39 pm

narfi wrote:
Tue Oct 30, 2018 4:06 pm
Capt UB wrote:
Tue Oct 30, 2018 2:52 pm
The tach it's self can be off by ???
I am so confused. I have never used one of these before, but if it is just a tiny computer counting induction pulses, how can it be off if it is setup properly? It just counts pulses and divides or multiplies those by a number you or the manufacture specify to give you an exact (not approximate) rpms?

I have used spoke counters on a bicycle when I was young (I think it was magnetic) to a digital display.
I worked with magnetic pickups plugged into a magnetos for a digitial display.
I have worked with light reflected on reflective tape for a digital display.
I have worked with a cheaper light reflected that just counts blades and you select 2,3,4 blades to calculate for a digital display.
And of course cables for an analog display.

Other than the cable and analog display, it seems the numbers should be straight forward x/y=z math like this isn't subjective is it?

I've not used a tach like this wraped around the cables, and I like learning things........ So how can x/y not equal z?
Does the weak spark not always register on the device or something? It seems this would give you sporadic readings, not something that was off by x% consistently.....

Your target is 950 and 5000-6000
You read 600 and 3000

https://www.tinytach.com/pdf/Tiny2AInst ... s11263.pdf
You have a steady reading, if it is idling smoothly in what 'feels' like the right range, the instructions tell you how to change the settings till you get the correct reading based on sparks per revolution. (8,6,4,3,2,1,1/2 sparks per revolution) It looks like your currently set at about 1.5x the one it should be set at..... for example if you have it set to 6 sparks per revolution you should change it to 4(from 60 to 90 degrees), if you have it set to 3 you should change it to 2.(from 120 to 180 degrees)
With those new settings you would end up with 900 and 4500 rpms and could then start making your adjustments.

Googling around find lots of interesting and conflicting information but people struggling.... so you certainly arent alone..... :P

Edit: the more I read the more I think you want to wrap around just one cable and select 2 sparks per revolution, if that cable doesnt work then try the other cable, some people reported that working for them.


Once again.....
Up date on TT setup on this OB (2017 Tohatsu 9.8 4 stroke)

2 cylinders, one power pack to two spark plugs, 4 stroke.

This is what TT help desk told me to do...

You need to read both waste spark and hot spark...

TT set to 360 and wrap both spark plug wires. May only need 1 or 2 wraps. I will be using this tach again so red wire is not cut.



Today on the river...

Just me
Tiny Tach TT 2AM
2017 Tohatsu 9.8 4 stroke

set at 360
4 wraps around one spark wire

out of gear in idle, about 600, should be 950

Don't think it's setup right..

3000 RPM
19.7 mph

Tohatsu prop 7.5 pitch

Running down the river into the wind, same down wind.

Only problem is the short shaft!!

I sent an Email to TT for help.


2 cylinders, one power pack to two spark plugs, 4 stroke.

This is what TT tach told me to do...
You need to read both waste spark and hot spark...

TT set to 360 and wrap both spark plug wires.


With TT wrap wires


May only need 1 or 2 wraps. I will be using this tach again so red wire is not cut.


There is a waste spark (weak) that is on the exhaust stroke, you need the hot and weak spark to get the right readings. On this OB, both spark plugs are powered by the same powerpack (coil). Wrapping both gives you the right reading.

I talked to Steve from Tiny Tach, great guy. He told me what to do.


Up date on TT setup on this OB (2017 Tohatsu 9.8 4 stroke)

2 cylinders, one power pack to two spark plugs, 4 stroke.

This is what TT tach told me to do...

You need to read both waste spark and hot spark...

TT set to 360 and wrap both spark plug wires. May only need 1 or 2 wraps. I will be using this tach again so red wire is not cut.


The waste spark output is not as strong as the hot output.
You add them up....

Just because the manufacturers say 950, you could have anywhere from 800-1050, so many things effect the rpm's. Throttle setup on the carbs, tiller or the remote! Fuel, age of motor, altitude and prevent maintenance! The tach it's self can be off by ???

The only base I have is being in idle, out of gear and being at around 950 rpms.

Getting it close so you can find the right prop is all you need.

7.5 pitch 20 mph @ 3000..... WOT.

Sounds about right on the prop and mph, rpm should be closer to 5000....?

I don't have the weight of the boat, but using 900 lbs. (me gear...) should give Tom something to work with. This Saturday, I'll run the river again and see what WOT reads in rpm's with the new tach setup.
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OrangeQuest
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Re: FS14 Wolf's build

Post by OrangeQuest » Tue Oct 30, 2018 6:30 pm

Ok I read the directions that Narfi posted from Tiny Tach. It is very simple. Where it seems to be confusing is the coil has two plug wires coming out of it. It doesn't say anything about wrapping the wire around multiple plug wires. Just one plug wire.
45° = 8 sparks per revolution 60° = 6 sparks per revolution 90° = 4 sparks per revolution 120° = 3 sparks per revolution 180° = 2 sparks per revolution 360° = 1 spark per revolution 720° = 1 spark per 2 revolution

The last setting should be it. 720 degrees should be an accurate reading. ONE plug wire sparks every 2 revolutions. It is a 4 stroke engine. I will let all of you think about that for a few minutes. Hint: the pick up wire doesn't read the "waste" spark because the pick up is not that sensitive. ALL 4 stroke motors with an ignition system fires the plug once per revolution. Once, at the end of compression stroke, very high energy going through the plug wire. Again at the end of the exhaust stroke with no energy because it has no path so the condenser stores it.
Last edited by OrangeQuest on Tue Oct 30, 2018 6:33 pm, edited 1 time in total.
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OrangeQuest
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Re: FS14 Wolf's build

Post by OrangeQuest » Tue Oct 30, 2018 6:32 pm

All other settings are for a coil wire that goes to a distributor or a 2 stroke engine.
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Capt UB
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Re: FS14 Wolf's build

Post by Capt UB » Tue Oct 30, 2018 6:37 pm

Update
Going to cut down transom for short shaft


Tiny Tach did not work, no matter what setting I used, wiring and settings...

Going to setup the transom for the 9.8 short shaft. The 7.5 pitch prop moved the boat at 20 mph. I'm happy with 20 mph with a 9.8 hp. I believe if I lower the OB I will be able to run cleaner and at a lower RPM and not WOT.

Starting tonight...
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Re: FS14 Wolf's build

Post by Capt UB » Tue Oct 30, 2018 6:39 pm

:roll: :roll: :roll: :roll: :roll: :roll: :roll: :roll: :roll: :roll: :roll: :roll:
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Re: FS14 Wolf's build

Post by Capt UB » Tue Oct 30, 2018 7:17 pm

So, I need to lower my OB two inches to be level with bottom of hull.

I have four inches from deck to top of transom.

This OB sits up high, so I can go down two inches without cutting the deck.
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Re: FS14 Wolf's build

Post by thb » Wed Oct 31, 2018 6:52 am

Bob,

I would just bite the bullet and cut two inches off the top of the transom and put layer of glass tape on top to protect the base wood.
Maybe wait to test boat before finishing off the cut surface in case you need to take more off or you need to cut through the back deck.

Regards
Tom

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Re: FS14 Wolf's build

Post by thb » Wed Oct 31, 2018 6:56 am

Bob,

I am not sure I interpreted your posting correctly. Is that picture of the motor after you already lowered it 2 inches?

What is with those funky cap screws?

Regards
Tom

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