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Mercury 1988 3 cyl

T

trynhooker

Regular Contributor
Working on a tach issue yesterday. Original tach has 6p 12 p setting. Newer tach from Teleflex only has 6p setting but says for Mercury the 6p setting will work.

We get about 7.5 volts from grey wire from wiring harness to tach when reading SEND to GND. The voltage increases/decreases with rpm.

Ign wire is 12 volts, gnd are good but we can't get the tach needle to move on the new tach. We even went back to store and changed to another new tach, same problem.

Can't figure out what the problem is other than the tach not having a 12p setting like the original tach does? Anyone?
 
If I am getting the variable voltage from the grey wire which coincides with rpm, wouldn't that mean the rectifier is operating correctly as far as putting out the correct voltage?
 
Here are a few issues from yesterday.

The rectifier has 2 yellow wires from the stator connected to each (alt.) terminal on the rectifier (the charging wires). The middle terminal on the rectifier (grey for tach) had no wire connected to it at all.
Oddly enough, the pigtail coming from the control box has a grey wire coming out, which was connected to the tach. That grey wire from this plug reads 7.5 volts and fluctuates up/down with engine rpm.
Do not know where that grey wire is getting it's power from because the main engine harness plug on the engine does not have a grey wire?

I did find the rectifier open on each terminal to gnd both ways so we're getting a new one.

One thing I don't have are the specs for this engine. When the engine is running, the 2 yellow wires connected to the rectifier read 7.5 volts +/-, and 21 volts +/-. Hopefully someone can tell me if those are the correct voltages from the charging coils on this engine.

The rectifier the engine has is 17602-1 which is now a 17602A 1.. Mercury confused the crap out of me. Some drawings show this as a terminal block with the engine having a voltage regulator (this engine does not have), other drawings show this as a rectifier.

http://www.boats.net/parts/search/M...THRU 9793576/Electrical Components/parts.html

Without a electrical diagram I cannot figure out what this engine is suppose to have?
 
Last edited:
Ok, customer just got the engine model, it is 0B166202

replacement rectifier is 8M0058226

This engine did not even have this type rectifier, it had an old 17602-a or a1, which in some places is called a terminal block...lol @ mercury
 
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