View Full Version : 70 HP ForceMercury converted Ignition

05-12-2009, 12:31 PM
"The Tach does not register at all from Idle to about 2500 RPM, then it Jumps to that rpm and seems to follow the engine. When backing off, it reaches about 2500 rpm and falls to zero. How do I check the Rectifier/Regulator? My Clymers Force manual does not seem to have this Info. I have replaced the tach, and same results."

05-16-2009, 04:10 PM
"Don, does your model have both the diamond shaped (black) 3 post rectifier that then feeds the regulator (box with the bunch of wires)??"

05-17-2009, 06:20 PM
"This unit has a square rectifier, with two yellow wires from the stator feeding it, and a red wire and a grey wire leaving. The red goes to the ignition while the grey goes to the tach. The red maintains a steady 12 volts, while the grey has about 11.9 volts when the tach is not working, and drops to about 9.4 when the tach is working. I have ordered a new voltage regulator/rectifier. Don"

05-17-2009, 08:15 PM
"The wireing you have discribed does not sound correct. The rectifier has two stator wires, a battery positive to recharge the battery and a ground. The tach should be wired to one of the stator wires, don't matter which one. Incorrect wireing will short out the rectifier. You may want to test the old rectifier before replacing, or you may short out the new one."

05-17-2009, 09:08 PM
"No, that doesn't sound right. If it's simply a rectifier it is NOT a regulated output."

05-18-2009, 10:48 AM
"According to Clymers it is a Rectifier/Regulator, and the motor wiring confirms what the schematic tells me. There are two yellow wires in, and a red and grey wire out. The Tach used to work fine, from the time I got the boat until now, wired the way the book shows, but now it doesn't, and that's why I wanted to be able to test the Rectifier/Regulator. Don"

05-18-2009, 12:43 PM
"Sorry, thought this has a complete Merc ignition. It kinda does, but once again a sorta cobbled version.

I can not find tests in the Merc service manuals for that particular regulator and at over 150 bucks you don't want to simply swap it out to see.

I've always disliked Clymers for exactly the reason that they don't contain the real information that you want.

Myself, I am unaware of another (free) source for the test proceedure that you are looking for."