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150 HP Johnson Tach Issue

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fisherman9985

Contributing Member
I have a 1995 150 HP Johnson Model # J150ELEOM. Just recently I had the boat professionally rewired and gauges replaced as well. Before having the boat rewired, the Tach worked for a while and then one day it just stopped working. I replaced the Tach and at idle it would register 1000 RPMS and when you accelerate, the reading goes to 0. I replaced the tach again thinking that I was a bad one and still the same issue. The voltage gauge is reading 12V with the engine not running, and 12.3 V while running which has led me to believe that the rectifier/regulator is defective. Before all this began, I was having problems with the motor overheating. Compression is 95,98,108, 110,110,105. Before I just go out and buy a new rectifier/regulator, any advise would be greatly appreciated.
 
you should get an ac reading on the two wires coming from the stator to the rectifier terminal block... after a minute of running at 2k rpm the voltage output on the red wire on the terminal block should be 14 to 15 volts dc....if you want to get serious the a dvd meter is required for stator output but just get the readings with a regular meter and get back to us..
 
The only problem with this would be is since the Tach is not working at the present moment how do I know where 2k RPMs would be to take the readings? Please advise? Also what color will the wires be that I need to take the reading from?
 
probably two yellow wires..they will be coming from under the flywheel...the exact rpm is not that important...but you want it above idle...you also don't want to over rev in neutral.....
 
I am not that good with electrical tasks so can you give me an idea on which wires need to be tested and on what setting on the meter? thanks.
 
Overheating can/will cause the water cooled rectifier to fail. Replace the rectifier and the new one will have one less wire(purple)
 
Another question pertaining to this engine.. Before I was having an over heating problem and the temperature sensors were going off so I had a new water pump installed, and also cleaned both port and starboard sides of the water passages out and replaced the orings behind the power heads and took it out today and the engine acted like it overheated i.e. Slow mode like it had been doing at wot but instead the engine went into slow mode and acted like it was overheating and but the temperature sensors didn't go off this time. So I used my thermal temp gun and tested all the cylinders and the temps were between 165-170 across all cylinders. So I don't have a true over heading problem anymore and I tested the temperature sensor again by grounding it out with the tan wire and that tested good. So which is leading me to believe that my power pack is bad. Could the power pack have anything also to contribute to the engines tach not working as well. As stated the engine this time acted as if it went into we're overheating and went into slow mode but wasn't per the temp gun. I am really just about had it with this motor and want it fixed. Please advise anyone.
 
Also as before as well I rani get the motor with my electronics as well today and left the bile gr pump on for a while by itself and got out of the boat for a a while and came back started the motor and starting driving by this time instead of it registering 12.4 v even though it should be above 13 running it was registering 11.3 v and by the time I got to the landing it was back st 12.4 so it is recharging the system but not fully please advise
 
http://www.cdielectronics.com/wp-content/uploads/2013/09/IS-113-4985.pdf
You need a DVA adaptor to properly diagnose the ignition and charging systems. If the stator is bad you should also put in a new regulator at the same time. It does have the slow mode you can force it by shorting the tan wire for the temp switch to engine ground, the horn should sound and it shouldnt rev above 2600 rpms. Your tach is definately stator related try switching yellow wires around and see if the tach works. If so the stator is probably bad.
 
have you had that battery tested?....a battery that reads 12.4 is not fully charged or is defective..a partial short in a battery can throw you for a loop when troubleshooting a charging system...always start trouble shooting in this area with a fully charged (12.7 volts) good battery...
 
papyson said:
have you had that battery tested?....a battery that reads 12.4 is not fully charged or is defective..a partial short in a battery can throw you for a loop when troubleshooting a charging system...always start trouble shooting in this area with a fully charged (12.7 volts) good battery...
Click to expand...

Battery tested fully charged... 12.8 Volts.. haven't haven't had a chance to do any electrical tests ie voltage meter for the charging system, but took the boat out again yesterday and he tach started working but not properly 4100 RPMS WOT and stopped working again during this time the voltage gauge was readin 14.1 Volts while running. I went ahead and ordered a new rectifier/regulator and also a power pack because the engine is also going into slow mode and the engine is not overheating. I used to thermal temp gun to verify this and also tested the Temperature sensor and the horn went off. The reason im thinking the power pack and not the temperature sensor is cause it the sensor tested good for the horn going off an also when it went into slow mode the horn did sound.
 
''The reason im thinking the power pack and not the temperature sensor is cause it the sensor tested good for the horn going off an also when it went into slow mode the horn did sound.''
I read this to say he horn sounded and the motor went into slow mode...is that correct?
 
papyson said:
''The reason im thinking the power pack and not the temperature sensor is cause it the sensor tested good for the horn going off an also when it went into slow mode the horn did sound.''
I read this to say he horn sounded and the motor went into slow mode...is that correct?
Click to expand...

Sorry for that didn't read it all after I wrote It before submitting the last reply, been up on duty with the marines all night at work. I meant when I grounded the tan wire for the Temperature sensor the horn sounded which means It working. When I was at WOT and the engine went into SLOW MODE, the horn didn't sound and the temps on the cylinders were normal temperature, which led me to believe it is the power pack causing this.

Question how hard is it to change out the power pack?
 
Childs play....disconnect the battery before you do it...label the old one ''spare'' before you remove it...
 
papyson said:
Childs play....disconnect the battery before you do it...label the old one ''spare'' before you remove it...
Click to expand...

There ain't nothing like I have to pull the flywheel or redo the timing on the motor for it is there also is it the same for the rectifier regulator easy??
 
So this evening i was able to install a new rectifier/regulator and also a power pack as well. Tested the motor on the water hose and the rectifier/regulator that I replaced fixed the problem with the Tach and the voltage gauge. could test out the power pack yet to see if the slow mode problem is resolved. Going out in the morning to run the boat and will report back with the outcome.
 
Update to the ongoing problem:
Took the boat out and the rectifier/regulator fixed the tach and voltage guage problem.
Replace the power pack and the engine is still going into slow mode and veriied again that the engine is not over heating with the thermal temp gun. also the overheat horn did not sound and verified that the horn and both temp senors are operational. Does anyone else have any ideas?
 
http://outboardparts.com/troubleshooting/troubleshooting3.htm
time to do a reset...check compression again...check to make sure spark will jump 7/16 inch with a gap tester...them put a inductive timing light in the boat and make sure all cylinders are firing and firing at the same frequency at time of failure..
.
4100 rpm is not slow mode..slow mode is around 2600.

so you have a basic problem....the determination is it fuel or fire?....please do the above and if it points to electronics then use the url data to trouble shoot....
..
 
papyson said:
http://outboardparts.com/troubleshooting/troubleshooting3.htm
time to do a reset...check compression again...check to make sure spark will jump 7/16 inch with a gap tester...them put a inductive timing light in the boat and make sure all cylinders are firing and firing at the same frequency at time of failure..
.
4100 rpm is not slow mode..slow mode is around 2600.

so you have a basic problem....the determination is it fuel or fire?....please do the above and if it points to electronics then use the url data to trouble shoot....
..
Click to expand...

well let me fix my last statement the tach is finally working but not totally working properly since I put the rectifier on. while on the water and in gear at WOT it will only register at most 4100 RPMS. if I put it in neutral I can rev it up past 4100 up past 5 k. At least the voltage gauge and tach are back to registering and working. At WOT the voltage gauge is registering 14.3 V that is good just don't know why it aint going back 4100 RPM's while in gear but will while reved and not in gear.

Now the engine does goes into slow mode. usualy when at WOT 30-45 sec into it the motor wil drop down to 2500RPMS and I have to turn it off for a minute like it had overheated but it obvisosly isn't.
 
I`m still not convinced the tach is working properly get a tach timing light and compare the tach reading. If you have a digital volt ohm meter that reads hertz you can use it to check engine rpms also. Stick the test probe in the pos port on the tester and hold it close to the #1 plug wire with the meter set at hertz. Multiply the reading by 60 gives you rpms.

Works pretty slick for a four stroke multiply by 120
 
Last edited:
kimcrwbr1 said:
I`m still not convinced the tach is working properly get a tach timing light and compare the tach reading. If you have a digital volt ohm meter that reads hertz you can use it to check engine rpms also. Stick the test probe in the pos port on the tester and hold it close to the #1 plug wire with the meter set at hertz. Multiply the reading by 60 gives you rpms.

Works pretty slick for a four stroke multiply by 120
Click to expand...


so your telling me do do this but which wire is the number 1 plug wire when there are 6 plug wires and also which end of that wire do i hold it at on the coil pack part?
 
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