RPM and Timing on 2 Cylinder Mercs

[mmf]

I don't have a 2 cylinder RPM guage but I do have an automotive Tach/Dwell meter but the lowest cylinders it will go is 4 cylinders. Is it possible to use it and divide the 4 cylinder reading by 2 or something? Anyone else done this?
Thanks

 

[daveswaves]

Re: RPM and Timing on 2 Cylinder Mercs

I don't have a 2 cylinder RPM guage but I do have an automotive Tach/Dwell meter but the lowest cylinders it will go is 4 cylinders. Is it possible to use it and divide the 4 cylinder reading by 2 or something? Anyone else done this?
Thanks

You don't say whether your ignition is points coil or cdi type coil, the dwell meters are designed to run on switched 12V. If you can get a reading at all
the rpm should be correct when set on 4 cyl as the 2 stroke fires twice for every once on the four stroke.

 

[mmf]

Re: RPM and Timing on 2 Cylinder Mercs

I guess I forgot about the type of ignition system which is CDI (Thunderbolt) around 1973 with the maker module (orange) under the flywheel. I wonder if someone makes an inductive pickup tach that will read off a coil like a timing light?

 

[mmf]

Re: RPM and Timing on 2 Cylinder Mercs

Found one,
http://cgi.ebay.com/ebaymotors/NEW-...Z170332568920QQptZMotorsQ5fAutomotiveQ5fTools

 

[7920hpMercury]

Re: RPM and Timing on 2 Cylinder Mercs

Another option I have had good luck with is a Tiny Tach.

Get the Tiny Tach that reads for 180 degrees or 2 sparks per revolution. These work great for a 2 cylinder 2 stroke outboard. Might have gone up, but I paid $25 a couple of years ago. They use these on rental lawn mowers and such for hours maintenance plus they have a digital readout for rpms's. You can also leave it installed if you want to.