Re: Tach for '69 Lark
Discussion, click here.
Schematic, click here
Bill greatly simplified the design, but I'm not 100% sure his reduction will work for all tachometers. But it should work fine for most, since it works with the most common tachometer integrated circuit out there. These designs use typical automotive type tachometers or (for better weatherproofing) marine inboard tachometers set to "4 cylinders". I like the marine inboard tachometers because they're only calibrated to 5 or 6k rpms, which is all you should be ever reving an old 40hp to. 8k is kind of useless if you get my point.
Unfortunately, I somehow lost byacey's simplification. But I've got an email out to him and I'll post it as soon as I get it.
The other option is to get an old airguide tachometer off ebay. But you must get one explicitly for 2 cylinder Johnson/Evinrude engines with magneto igntion. There's plenty on ebay that are missing their senders, the seller doesn't know what exact outboards they work on, etc. Those are totally useless.
