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b98 two stroke 90hp tachometer question

G

gone_postal

Regular Contributor
"My boat is equipped w/ Faria

"My boat is equipped w/ Faria gauges and the tach has the warning lights built-in. My current tach registers idle speed to an extent, but never goes over 1500RPM - it jumps when revved, drops when back to idle, but never seems to exceed 1500, so I assume my signal & wiring are good and the tach is bad.

I bought an identical gauge from a surplus store on Ebay - brand new - '96+ Johnson it was stated. They are identical w/ the exception of the last two numbers in the model number, but I assume it's a different revision, manufacture date, etc. The new tach's warning lights turn on during system check when I first turn the key and it beeps, but the needle never moves. It is in the exact same spot it is in in the auction's picture. It's an idiotproof install (i think) - the 8pin wiring harness and setting the selector dial to 6 for my particular motor (only other option is 5).

Any ideas? Defective tach? Is there some sort of safety lock on the mechanism somewhere to keep it from moving during shipping?"
 
"You might want to check out y

"You might want to check out your original tachometer with the following test. However, it will be necessary to splice into one of the "yellow" stator wires as I believe your engine does not have a terminal block as listed with my instructions. Something to think about.

(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

Remove that gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
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