1988 Johnson 150GT tach issues

[WILLIAMHARDEN]

I have read and followed several posts trying to resolve my issues before asking. Last year I replaced Rectifier and Stator, after a small fire on the water. Now my tach just went out. I tried connecting grey wire to yellow wire with grey stripe at the circuit board and still no tach. Bought a new Teleflex tach, installed with 6P selected and still no tach. Did a multimeter check on grey tach wire and have solid connection from motor to tach (send). Checked charging system and battery checked out at 12.44 off. Started motor and got a constantly changing reading that dipped to 12 but occasionally jumping to 17-18. Very hard to get an actual reading. Oh, I do have power at tach but no reading with motor running. HELP!! I'm ordering repair manual but have limited time to repair before July 4th camping trip that starts next week. Thanks for any comments, William

 

[ezeke]

Re: 1988 Johnson 150GT tach issues

I have read and followed several posts trying to resolve my issues before asking. Last year I replaced Rectifier and Stator, after a small fire on the water. Now my tach just went out. I tried connecting grey wire to yellow wire with grey stripe at the circuit board and still no tach. Bought a new Teleflex tach, installed with 6P selected and still no tach. Did a multimeter check on grey tach wire and have solid connection from motor to tach (send). Checked charging system and battery checked out at 12.44 off. Started motor and got a constantly changing reading that dipped to 12 but occasionally jumping to 17-18. Very hard to get an actual reading. Oh, I do have power at tach but no reading with motor running. HELP!! I'm ordering repair manual but have limited time to repair before July 4th camping trip that starts next week. Thanks for any comments, William

You need two things for the tach to work, a good signal through the gray wire and a good solid engine ground on the black wire.

 

[WILLIAMHARDEN]

Re: 1988 Johnson 150GT tach issues

Ground is good and continuity check was good on the grey send wire. I just watched video of AndyinNY on the forum page where his multimeter is jumping all over the place with motor running just like mine. Can the ignition switch cause any of these problems since the grey send wire does go to the ignition before ending up at the tachometer?

 

[emdsapmgr]

Re: 1988 Johnson 150GT tach issues

Not sure just what rectifier you replaced. The XP/GT models have the large 35 amp charging system and that model uses the combination rectifier/regulator that is located in the block under the vented flywheel and is cooled by the block water. Perhaps that is the one you had replaced. The grey tach lead should not be routed through the key switch. It should feed directly to the three wire tach lead along with the power and ground. The original factory service manual provides various tests for both the stator and the rectifier/regulator.

 

[WILLIAMHARDEN]

Re: 1988 Johnson 150GT tach issues

Yes it was the water cooled rectifier under the flywheel. CDI brand. Sorry for wrong info on wiring, I thought the wires were coming from ignition but actually come out of harness by the ignition. Three wires (grey,black,purple)go into plug and drops to one orange wire coming out other end of plug going to either speedo or trim gauge. The grey splits right before plug and goes to tach. This wire passed continuity check from motor to tach. If no one has the miracle answer, looks like a trip to the master mechanic. Between my work schedule (gone 15hrs a day) and the delivery of the repair manual for my boat, I may be out of options before our upcoming camping trip. Thanks for all replies and suggestions.

 

[WILLIAMHARDEN]

Re: 1988 Johnson 150GT tach issues

Great. I took the cheap multimeter back to WalMart and purchased a good one. Readings from battery while running stayed around 12.25. Looked over the instructions for checking rectifier again and found my error. I was trying the wrong grey wire because when I connected the other grey wire to the yellow my tach started working. Looks like I'll be replacing the rectifier AGAIN. As high as they are looks like the family fun on the lake is over this year. Unless anyone knows where I might get one fairly cheap? Thanks for all who replied/reply.
William

 

[WILLIAMHARDEN]

Re: 1988 Johnson 150GT tach issues

If anyone has a used Rectifier part # 583268 OMC or # 193-5204 CDI or # 9-17203 Mallory or even # 18-5825 Sierra please let me know.