Reading 2-stroke rpm with multimeter?

[phralh]

Did some reading on the web and found an article on how to read rpm's with a "car"-multimeter with rpm function. I was thinking of trying this on my '75 evinrude 9.9. As I understood the article, you hook up one cable to stopswitch cable (leads to breakerpoint) and the other to ground. Of course most meters are made for 4-stroke engines, but results can be recalculated to correct reading.

To recalculate a 1cyl 2-stroke - select 2cyl 4-stroke setting
To recalculate a 2cyl 2-stroke - select 4cyl 4-stroke setting

Am I doing the math correctly? Would this work?

Thanks
//Fredrik

 

[Vic.S]

Re: Reading 2-stroke rpm with multimeter?

Yes I think so but your outboard has two sets of points, one for each cylinder, so you would, I think, have to use the reading for a single cyl 2 stroke/ 2cyl 4 stroke.

The car ignition system will be driven fro a 12 vot battery but the o/b is only powered from its mag. The volts the meter sees may or maynot be high enough to drive it.

Worth a try though.

 

[asdasc]

Re: Reading 2-stroke rpm with multimeter?

How does everyone read RPM on a magneto based outboard?

Are there special meter available? Are the expensive?

 

[kandil]

Re: Reading 2-stroke rpm with multimeter?

I use a hour/rpm meter you can get on ebay for under $40

 

[tashasdaddy]

Re: Reading 2-stroke rpm with multimeter?

tiny tach.com great for set ups, and then not worry.

 

[asdasc]

Re: Reading 2-stroke rpm with multimeter?

Wow, those are neat and easy to use! Thanks TD.

 

[Vic.S]

Re: Reading 2-stroke rpm with multimeter?

But note that the lithium battery is not replaceable. When the battery expires the Tiny Tach is dead!

 

[Sea18Horse]

Re: Reading 2-stroke rpm with multimeter?

How does everyone read RPM on a magneto based outboard?

Are there special meter available? Are they expensive?

asdasc brings up a good point. Are the voltages produced by a magneto similar enough to regular 12 volt points that the meter could make sense of them? Just have to try it and find out I guess. May still need something like a tinytach to verify your readings though :redface: .

VicS. wrote;

"But note that the lithium battery is not replaceable. When the battery expires the Tiny Tach is dead!"

Hmmmm, I wonder how long they're lasting. For my needs it wouldn't be used regularly anyway. Only when a new (to me) motor is run or after a major change.

Cheers..............Todd

 

[asdasc]

Re: Reading 2-stroke rpm with multimeter?

Their website doesn't mention that they are not replaceable! I would think they could easily be replaced. They do mention that they are Lithium, and that they should last years plus of regular use.

My buddy has a motorcycle tach that I was going to try. I will let you know how that turns out whenever I get to it.