TOPIC: 1964 500 50 hp low idle-WOT tachometer?

I am still playing with the controller cable settings trying to find a balance between a low idle and being able to have the throttle open all the way. It appears that one cannot do both with this old controller and motor. The controller only allows so much cable movement. Anyway…I am looking to add a tachometer to my 1964 500. It seems like useful information when running an engine, especially an antique motor. The chances of finding an original tachometer does not seems likely.

I looked on ebay and found these digital tachometers that say they will work with any 2 stoke 4-6-8 cylinder engine. $12 made in China– go figure. It only has 2 wires. One wraps around a spark plug wire and the other is a ground.

Can this possibly work? It could only register when one cylinder receives an electrical signal to fire the spark plug. I would love a low cost solution that actually works…gives accurate engine RPMs. I am not optimistic that these are in anyway useful.



Suggestions or comment are welcome.

Email sent on tach, I'll let the "Merc-a-holics" help with the throttle cable issue.

call me for the cable connection.
Dave 1 914 310 7086.

I tried a "Tiny Tach" once and it was a joke. It works by induction, as the one you describe. I asked tiny tach if it would work on multi cylinder engines & was told it was OK. Well, it didn't work. The "pickup" wire is not shielded, so it picked up induction from all of the plug wires. Useless. I'd find a tack for a 4 cylinder 2 cycle with a magneto. It must be for a magneto to work. They aren't that uncommon, but you will need to sniff around some. Ebay is best bet, or maye a fellow Merc person is willing to dip into their stash & sell you one. Any brand will work, as long as the application is correct.

A tachometer set up to read a 12 pole alternator wouldn't work? I guess it would have to be the E or EL model, please pardon my lack of knowledge here guys. Just wondering...

i sheild mine with aluminum foil and tape to make it work. just hard to see in the sun.