Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor? The
auto engine is 4 cycle, and the boat engine is 2 cycle.

I'm just wondering what it take to make it useable on the o/b.

the tack will be off by 2x since the 2stroke fires 2x as often... and the tachs
pick up on when the coil sends voltate..

at least; that's my take on it.... as compared to trying to rig a car tach to a
2cycle race bike.

On Fri, 19 Mar 2004 15:10:55 -0600, "RB" wrote:

Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor? The
auto engine is 4 cycle, and the boat engine is 2 cycle.

I'm just wondering what it take to make it useable on the o/b.



---
Remove x's to send.

Some tachs allow you to select 4,6 or 8 cylinder.. If you OB is 4 cylinder 2
cycle, couldn't you select 8 cylinder and that would allow for the 2x
situation??

Maybe I'm wrong, often am..

Steve
s/v Good Intentions

Plenty of reasons.....

1) car has ONE ignition coil that fires twice on ever revolution that
comes from a 12V power source and points....or a trigger coil on
electronic ignitions.

1A) The outboard has one coil for every cylinder, like my 175HP
Mercury 2.5L V-6 Sport Jet or one coil for every two cylinders and
just fires both spark plugs as one of the plugs is in an open exhaust
cylinder (jetskis are this way). The power for these comes from a
400V pulse loading coil of a permanent magnet magneto, just like it
did in 1934. There's no low-voltage side to it, so it will blow the
hell out of the car tach, no sweat....

Now, how about a Tiny Tach for it. Runs off a tiny watch battery for
years and even has a useful hour meter. You simply wrap the sensor
wire around ONE spark plug wire with no actual connection. It senses
the ignition pulses from ANY engine, 2 stroke or 4 and any number of
cylinders. This turns on the hour meter and the display, after you
tell it what kind of engine it is "near" simply tells you the RPM
digitally and VERY accurately.

Cheap! Quick and no connections to the EXPENSIVE ignition computers!

http://www.tinytach.com/tinytach.html

Had one that outlasted THREE jetskis! Completely sealed epoxy
enclosed.....worked great, always. Too bad the jetskis didn't...(c;



On Fri, 19 Mar 2004 15:10:55 -0600, "RB"
wrote:

Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor? The
auto engine is 4 cycle, and the boat engine is 2 cycle.

I'm just wondering what it take to make it useable on the o/b.




Larry W4CSC
POWER is our friend!

That's a slick instrument. Wish I had known of it for my old boat powered by
an outboard.

"Larry W4CSC" wrote in message
...
Plenty of reasons.....

1) car has ONE ignition coil that fires twice on ever revolution that
comes from a 12V power source and points....or a trigger coil on
electronic ignitions.

1A) The outboard has one coil for every cylinder, like my 175HP
Mercury 2.5L V-6 Sport Jet or one coil for every two cylinders and
just fires both spark plugs as one of the plugs is in an open exhaust
cylinder (jetskis are this way). The power for these comes from a
400V pulse loading coil of a permanent magnet magneto, just like it
did in 1934. There's no low-voltage side to it, so it will blow the
hell out of the car tach, no sweat....

Now, how about a Tiny Tach for it. Runs off a tiny watch battery for
years and even has a useful hour meter. You simply wrap the sensor
wire around ONE spark plug wire with no actual connection. It senses
the ignition pulses from ANY engine, 2 stroke or 4 and any number of
cylinders. This turns on the hour meter and the display, after you
tell it what kind of engine it is "near" simply tells you the RPM
digitally and VERY accurately.

Cheap! Quick and no connections to the EXPENSIVE ignition computers!

http://www.tinytach.com/tinytach.html

Had one that outlasted THREE jetskis! Completely sealed epoxy
enclosed.....worked great, always. Too bad the jetskis didn't...(c;



On Fri, 19 Mar 2004 15:10:55 -0600, "RB"
wrote:

Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor?
The
auto engine is 4 cycle, and the boat engine is 2 cycle.

I'm just wondering what it take to make it useable on the o/b.




Larry W4CSC
POWER is our friend!

With the restrictions others added here about multi-coil systems, it can
work.

I've done the opposite on my boat; I got a nice tach cheap but it was
8000 rpm max, so I run it in "4 cylinder" mode and it reads 4000 RPM max.
A few stick-on numbers inside and it Works For Me.

Some tachs allow you to select 4,6 or 8 cylinder.. If you OB is 4 cylinder 2
cycle, couldn't you select 8 cylinder and that would allow for the 2x

--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?