90 HP Tach Rectifier Problem

[MrTuna]

Just bought this boat - 1992 Johnson 90 HP - 1st things 1st tossed the water pump and Stats - engine runs like a champ - smooth idle smooth high rpm, plenty of power -<br /><br />OMC Tach not working - 12V at Tach Purple and Black poles - good read <br /><br />My question is with the reading of pulse - From the searches I have done it seems with a Multimeter set on the AC Scale of (15) I should read 5 to 7 volts with black to ground and red to Gray wire - I get zip on the multimeter - I then went to the terminal board on the engine. I disconnected the feed to the tach - I checked the gray from the rectifier again with the AC scale set to 15 & read Zip - I moved the red pin of the multimeter to both yellow wires on the terminal board & read 7.5 Volts AC and 11 Volts AC - I'm not sure what I should be reading on those - <br /><br />Any ideas - anything I'm doing wrong here ????

 

[TD_Maker]

Re: 90 HP Tach Rectifier Problem

Replace the rectifier. Problem solved.

 

[MrTuna]

Re: 90 HP Tach Rectifier Problem

Well unfortunately the new rectfier did not solve the problem - I am using a radio shack meter - for those familiar with the wiring the top 2 posts of the wiring block are the 2 wires from stator - yellow & the other yellow gray - on the ac scale I read 7.5 to 10 volts on either wire - I can also hook up the gray wire that goes to the tach to the solid yellow of the stator & the tach works fine this was suggested somewhere else to check tach - With this same meter I get nothing from the gray (pulse wire) zero reading and gray from rectifier hooked to gray of tach - tach does not work. I isolated the red wire - took it off terminal block coming from rectifier. On the red wire from the rectifier I read 5 Volts DC - what i don't understand is it joins on the terminal a wire carrying 12V DC - that source is unknown to me - Any ideas ?????

 

[MCM]

Re: 90 HP Tach Rectifier Problem

Which terminals are yellow and yellow/gray of the rectifier connected to?

 

[MrTuna]

Re: 90 HP Tach Rectifier Problem

From the top of Terminal # 1 there is a solid yellow wire from the stator joining a solid yellow of Rectifier - Terminal # 2 there is a yellow gray from stator joing yellow gray of rectifier

 

[MrTuna]

Re: 90 HP Tach Rectifier Problem

Just in case anyone has this problem I am posting the fix to my particular problem - MAKE SURE YOU HAVE 12V at the Purple wire on the terminal going into the rectifier - When you turn the key switch on you send 12V to the dash gauges and then 12V to the engine via another purple wire which goes to the terminal on the block. I had 12V up to the "red connector" and believe it or not 1 inch after - then no current - The wire looked perfect on the outside - Cut the wire & all copper disintegraded - all blackened etc - ran a new wire from the dash purple to the terminal & all is well - Hope this helps someone - simple continuity tests of the purple wire carrying 12V - when the 12V went into the rectifier the gray pulse delivered to the tach -