1990 GT-150, tach quit working... 1990 GT-150, tach quit working...
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    1990 GT-150, tach quit working...
from Mike B (  
12/18/2006 2:34:00 PM


 I have a Champion 184 with a 1990 Johnson GT-150. My tach recently stopped working, and reading around here, I'm concerned it may be the rectifier. I checked the voltage at the tach, the red wire is spitting out voltage (like in the 13's) and the gray wire is not. Checked the battery: At idle it has 13.60 volts, and 14.20 volts at around 1500 rpm (I have no tach) and revved higher it would hit 14.30.

When I engage the ignition, the tach jumps, but does not move when the motor turns over or is running. It gave out yesterday and jumped up only a few more times.

2 questions in addition to "what do you think is wrong with it?"

1. Does this motor have the 35 amp charging system?

2. Where is the rectifier? I can't find it and my shop manual is absolutely useless.


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   tach problems from Stratos1 (  12/18/2006 2:49:00 PM
 Good question Mike i have a 90 Johnson 175 that has the same problem. If you figure it out shoot me a E-maill if you dont mind.

   Tach from Ed (  12/18/2006 8:36:00 PM
 My 1990 XP150 tach has been doing this for about a year. My mechanic told me it was the rectifier. 35A Charging system? I don't know. The flywheel has to be removed to replace the recitifier but I do not know exactly where it is located. Hope this helps.

   Rectifier... from Mike B (  12/18/2006 9:15:00 PM
 I did some trouble shooting and it looks to be the rectifier. I have one in the mail and I'll let you guys know how it turns out.

   use a voltmeter from Cajunearbass (  12/18/2006 9:49:00 PM
 to see how many volts you are getting with the motor idiling.hook it to your battery and you should be getting somewhere around 14.5 volts if it is reading a lot higher it is probably the rectifier. you need to check because i had the same thing happen but mine turned out to be the voltmeter and cost me $165 for nothing. most places will not take back electrical componets.i traded the boat off and sold the rectifier on ebay for a lot less than what i gave.

   Retifier is not under flywheel from humminbird  12/18/2006 10:10:00 PM
 Trace the yellow leads from under the flywheel to the rectifier. From the rectifier there should be red and gray (tach) leads with the red leads going to the solenoid switch and the gray lead going to the tach. Hope this helps in locating the rectifier.


   Rectifier... from Mike B (  12/19/2006 10:49:00 AM
 Humminbird, it appears to be under the flywheel, and this is what my mechanic told me. It is water cooled and sits in a slot under the flywheel and the stator with. It has a red, gray, yellow and purple wire coming from it. I believe the voltage regulator is built in.

Apparantly the reason it sits here is because of the high output charging system present with the GT-150 (35 amp vs. 6 or 10). The shop manual I have says the rectifier is on the side near the terminal block in most of the OMC motors of this era, but that book is worth nothing but tinder to start a fire.

Putting the rectifier there makes as much sense as the starter on a Cadillac Northstar (Under the whole intake assembly, on the top of the engine block) but I'll deal with it.

Also, is there harm to run without the rectifier? My mechanic told me a way to check the rectifier is to check the voltage of the gray wire that leads to the VRO system, and I got spooked when I found it may be tied in with oiling. I do not want to blow the motor, but I ran it full bore about 5 minutes before I knew of this little tie-in. I assume things must be fine if I didn't hear all sorts of fun mechanical metal grinding noises!

   Seahorse from BigAl (  12/19/2006 1:36:00 PM
 I would just about bet that Mr. SEAHORSE can answer almost any question you might have about where/what a rectifier is and color of wires. Haven't read a post in a long time from him but if he answers I would tend to read closely.

   rectifier from Cajunearbass (  12/19/2006 8:16:00 PM
 is under the flywheel on a gt 150

   re-rectifier from Cajunearbass (  12/19/2006 8:20:00 PM
 you have to pull the flywheel. what does your voltmeter sit on while idling . as i said . take a voltmeter and hook it to the battery while idling.if the voltage is high it is the rec . if not more than likely a gauge. the flywheel is not that hard to pull if you have a puller.

   My bad from Cajunearbass (  12/20/2006 8:27:00 PM
 I should have read your post all the way through.only excuse is i have a habit of getting sleepy while on the computer.



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