I need a small in-dash tachometer

[BWR1953]

I've been seriously thrashing the web for a 2" diameter tach which can mount in my dash and work with a 2-stroke motor. So far, no joy. I've found a few automotive tachs which would fit, but can't handle 2-stroke engines.

There is very limited space on the dash for the tach. I suppose I could mount one on top, a la '69 GTO, but that would be inappropriate. :lol:

Looking for a little help! :joyous:

 

[QBhoy]

Have a look at tiny tach

 

[BWR1953]

Have a look at tiny tach

I already have a clone of one of those. It's pretty flaky. Switches configurations right in the middle of running a test.

And I'm looking for something with a standard permanent mount that can I wire into my harness. Those temp tachs don't fit the bill. :grumpy:

 

[sam am I]

What engine type/manu is your 2-stroke?

 

[Scott Danforth]

there is a 2" engine monitor for a suzuki https://www.v3electronicsusa.com/wp-content/uploads/2019/12/Sterling-2019-grp-v2.pdf

Faria made a 2" tach for certain boats, however i believe they were all V8's

 

[BWR1953]

What engine type/manu is your 2-stroke?

It's a 1985 Mercury 50HP outboard.

 

[BWR1953]

there is a 2" engine monitor for a suzuki https://www.v3electronicsusa.com/wp-content/uploads/2019/12/Sterling-2019-grp-v2.pdf

Faria made a 2" tach for certain boats, however i believe they were all V8's

I didn't see anything in the Suzuki brochure. I've seen the Faria gauges and yeah, they were all V8s. I've also seen small gauges for diesels as well.

 

[Scott Danforth]

The suzuki gauge needs the ECM on the motor to drive it

you could use the 2" faria gauge, use a mag pickup, like used on a diesel, and install 4 screws in your flywheel. That would give you 4 pulses per revolution

 

[BWR1953]

The suzuki gauge needs the ECM on the motor to drive it

you could use the 2" faria gauge, use a mag pickup, like used on a diesel, and install 4 screws in your flywheel. That would give you 4 pulses per revolution

Hmmm...

 

[Scott Danforth]

Couls also have sam am I sketch up a signal conversion schematic to take the ignition pulses from the OB and convert to the sinking signal to trigger the tach

 

[sam am I]

BWR1953 Does that motor use that autoblend system?

 

[BWR1953]

BWR1953 Does that motor use that autoblend system?

Nope, it's pre-mix.

 

[BWR1953]

I found a video last night where a guy built a converter to allow using a standard automotive tach. I'll be looking into that for sure.

 

[sam am I]

Hold the phone!!

That "converter" is just a signal conditioner...........

AND,

*Tohatsu 18HP 2 stroke stator is 4 pole = 2 pulses/rev (recall electrical pulses per revolution are equal to 1/2 the number of alternator poles.)

AND,

A 4 stroke, 4 cylinder engine puts out 2 pulses/rev!!! Note in the video he's set his 4 stroke tach to, "4 cyl". (For 4 stroke engine.....1 cyl = 1 pulse/2 rev, 2 cyl = 1 pulse/rev, 4 cyl = 2 pulse/rev, 6 cyl = 3 pulse/rev, 8 cyl = 4 pulse/rev, 10 cyl = 6 pulse/rev)


Soooooooo......in English?

A guy (him) can use/get away with using a 4 stroke tach set to "4" on a(his) 2 stroke Tohatsu because its (his) stator puts out 2 pulses/rev just like a 4 cylinder 4 stroke....LUCKYYYYY!!

He therefor is just "conditioning" the signal and really doesn't even need that "converter".......

You have a 12 pole stator = 6 pulse/rev.............You'd need a 4 stroke tach that had a "10" cylinder setting (10 cyl = 6 pulse/rev)

*http://www.projectk.co.jp/marine/pdf/faria_tacho.pdf (See page 3)

 

[Scott Danforth]

or use a mag-pickup that normally reads flywheel teeth on a diesel. and have mounted so it reads 4 bolts in the flywheel to give 4 pulses per revolution. that will mean a 8 cylinder 4-stroke tach would work for the application

or the tach could be pulled apart and the output of the D/A converter adjusted to read properly since the small 2" tachs do not have a cylinder switch setting

 

[BWR1953]

Hold the phone!!

That "converter" is just a signal conditioner...........

AND,

*Tohatsu 18HP 2 stroke stator is 4 pole = 2 pulses/rev (recall electrical pulses per revolution are equal to 1/2 the number of alternator poles.)

AND,

A 4 stroke, 4 cylinder engine puts out 2 pulses/rev!!! Note in the video he's set his 4 stroke tach to, "4 cyl". (For 4 stroke engine.....1 cyl = 1 pulse/2 rev, 2 cyl = 1 pulse/rev, 4 cyl = 2 pulse/rev, 6 cyl = 3 pulse/rev, 8 cyl = 4 pulse/rev, 10 cyl = 6 pulse/rev)


Soooooooo......in English?

A guy (him) can use/get away with using a 4 stroke tach set to "4" on a(his) 2 stroke Tohatsu because its (his) stator puts out 2 pulses/rev just like a 4 cylinder 4 stroke....LUCKYYYYY!!

He therefor is just "conditioning" the signal and really doesn't even need that "converter".......

You have a 12 pole stator = 6 pulse/rev.............You'd need a 4 stroke tach that had a "10" cylinder setting (10 cyl = 6 pulse/rev)

*http://www.projectk.co.jp/marine/pdf/faria_tacho.pdf (See page 3)

or use a mag-pickup that normally reads flywheel teeth on a diesel. and have mounted so it reads 4 bolts in the flywheel to give 4 pulses per revolution. that will mean a 8 cylinder 4-stroke tach would work for the application

or the tach could be pulled apart and the output of the D/A converter adjusted to read properly since the small 2" tachs do not have a cylinder switch setting

Ah, jeez. If figures that it can't be simple.

Okay, thanks.

Now I'm gonna go work on my truck. :lol:

 

[Scott Danforth]

Now I'm gonna go work on my truck. :lol:

what kind of truck??

 

[sam am I]

Correction to #14, 10 cyl = 5 pulses/rev NOT 6 pulses/rev

 

[BWR1953]

what kind of truck??

 

[BWR1953]

Here and here

It's a 52MM (2 1/16") and does 10 cyl (6 pulses/rev, your stator), hook it to one of your stator's two charge winding wires.

Thanks! I'll check it out. :joyous: