Dwell Tach question.

[Moody Blue]

Going thru an old box recently I came across a piece of test equipment I had bought some25-30 years ago. Had forgotten I still had it and now am wondering if I can use it as a "shop tach" to verify the RPM of my 1971 Merc 800 4 cyl outboard. It has a distributor but no points. It uses the CD electronic ignition.

The dwell tach has a button for 4/6/8 cyl.