Auqameter Tach is functioning incorretly on my 1971 Johnson 85

[MWatts9728]

I picked up a 1973 crestliner recently the boat is solid & runs great but it also got a laundry list of troubles. Monitoring the engine is important and the Tachometer isn't functioning properly. I need help! I assume the tach is operable but it reads all wrong. At idle which sounds like a normal rpm range for idle it reads between 4 & 5,000 rpms. I assume the tach is set wrong. I have seen from other post that 6 should be my normal setting. Assuming my tach is most likely set to 1 (4,500 rpm current reading / 750 normal operating range = 6) How do I adjust it? I dont see anything on the back of the tach under the dash. At the bottom of the front partcially under the bezel it reads "Auqameter FS074-11 idst corp". The outboard is a 1971 Johnson 85 ESL-71A. Oh 1 more thing that may effect the situation the motor has been converted to electronic ignition. Any advice? I have no experiance with Tachometers.

[F_R]

I have no idea what your Aquameter requires. But many of them required a transmitter. Nevertheless, if there is no pulse switch on the back of it, it either is defective or else it just is not applicable to your motor. Your motor requires an alternator-driven tach, which nearly all outboard tachs are nowadays. The ignition system is not involved with an alternator tach. Yes the correct setting is 6 pulses. Your best bet is probably just get a new tach. If you can identify what yours was made for, it may be valuable to somebody.

Hm.m.m.m.m., I wonder what kind of electronic ignition your motor has been converted to? It came with the battery CD electronic ignition. Are you still using the distributor under the flywheel?

[emdsapmgr]

I ran one of these tachs on my 1976 75 Hp Evinrude. It is a nice instrument, make like a fine watch. My tach had only two black wires, no tach switch for variable setting. It believe it was directly connected to the grey wire in the control box, the other wire direct to ground. Seemed to be spot on at all rpm ranges. I'm more familiar with today's more current marine tachs-was always amazed that this tach worked the way it did. The engine this was connected to had a stock factory 12 pole stator to drive the tach. You may want to confirm where you are getting the tach signal from-it needs to be from one of the connections on the electrical terminal block on the main electrical bracket. The normal tach signal should come from the engine's stator, not the new electronic ignition.