I am trying to get a tach working on a new to me J90TSLEU. It has an unregulated charging system. I took a tach I had from a '89 Evinrude 40 hp and tried to use it. It had been acting erratically on the 40, usually reading way high randomly, then going back to normal. It did pretty much the same thing on the 90 so I figured it was bad. I bought a new Teleflex Amega model 58255P. The application chart says it will work with "Evinrude / Johnson, All V Models" At the bottom of the chart it says "Johnson / Evinrude 88 - 112 SPL models may require the addition of a 2000 ohm resistor or a BRP regulator." The installation instructions do not mention this resistor or where to install it. I called Teleflex tech support, and was told to place it inline with the signal wire, then the tech called me back and said he made a mistake and to put it inline with the ignition (purple) wire. I did this and the tach did not work at all, not even go to zero when swithced on. The voltage after the resistor was about 2.8. I removed the resistor and the tach seemed to work OK on muffs at idle and high idle. On the water, idle and at no wake speed it seemed OK. When I opened it up, tach climbed up and at what I guess was 4000 - 4500 rpm it dropped down to read 1200 or so, when I backed down to cruise speed, guessing 3500 - 4000 rpm, the tach climbed up to full scale, 7000. It did this several times. I reinstalled the resistor in the ign. wire and the tach does not work at all.
Searched other erratic tach posts here and they usually point to rectifier problems. My rectifier checks out good with ohmmeter test per service manual. I did not try to heat the rectifier to see if results change. All connections and wiring are good.
Does anyone know where to connect the 2k ohm resistor, if in fact it is required? The tach instructions say it "may" be required. Or do I need a regulator? If so, do I replace my rectifier with the BRP rectifier/regulator from the higher output stators, or is a seperate regulator available as an add-on?
Any other tricks to install tach on SPL engines before I call Teleflex again?
Oh, the selector on the tach is set to 6 per service manual and tach instructions.
I'm trying to figure out what prop pitch I need for this boat/ engine, plus I just like having a tach I can trust.