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Johnson 50hp tach problems

Tb3625

Member
If you don't want to read the background info on this motor skip to the 2nd paragraph.
My 1999 johnson 50hp model J50PLEEA has was not running right as of a couple weeks ago. I rebuilt the carbs because they had crap in them, I used a rebuild kit cause the gaskets were all old and cracked. There was also a spark jumping around the boot and grounding at the block when it was running, so I replaced both plugs , the wires and boots and it took care of the problem. The old boots were stretched and the new boots were much more snug. Tried starting the motor and it idled okay at best. Took it out on the water and it surged at WOT. My friend pumped the primer bulb while running and it stoped surging. So I got rid of the vro pump and converted it to a normal fuel pump, I always premixed anyways. Tried to start it and it wouldn't idle. I opened up the carbs to find little pieces of black rubber from either the old vro pump diaphragms deteriorating or pieces of fuel line. I replaced all the fuel lines and then cleaned out the carbs again. Started it up today and it idled pretty good.

Then I look at the tachometer and it wasn't working. When I turn the key for power the needle bounces a bit and then when the motor start the needle barley moves to 200rs. The tach has always worked good and then all of the sudden today it does this. I checked the voltage to my battery while the motor was idleing and my battery voltage doesn't change with the motor running. So the motor is not charging the batteries. Also I used a multimeter to check it, and tested on the diode setting on the voltage regulatorRed to yellow .503v
Red to 2nd yellow .506v
Red to grey. 1.907v
The purple wire when attached to everything else shows zero.


I have done some research and the tach not working points to my voltage rectifier being the problem. Is there anything else it could be beside the rectifier?
I keep chasing problem after problem and am tired of throwing parts at it.
Thanks in advanced for any help!!!!!!!
 
Is there a surefire way to test the stator? Also the motor idles fine right now, if the stator was bad wouldn't the motor not run?
 
There two different circuits in the stator. One for battery charging and one for ignition for the motor. Procedures are in the service manual for testing.
 
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The purple wire has to have 12V on it ,if not it wont turn rectifier/regulator on....

I didn't test the rectifier/regulator on the motor, I tried to bench test it with a multimeter on the diode setting. I tested all connections with the positive lead and negative lead on each wires and then switched the positive And negative leads. I got no reading at all for anything between the purple wire and anything else.
 
You need to test that unit with a load bank. Hook it back up and see if you have 12V on purple wire with key on. See what battery voltage is reading and turn everything electrical on boat on and voltage should increase.
 
I'm going to try and locate parts to build a DVA or find somewhere local to buy one. When I use the DVA to test the stator can I just attach it directly to the different leads on the terminal block?
 
http://www.cdielectronics.com/wp-content/uploads/2014/03/IS-173-4560.pdf
Be sure the charging system is working good before putting it into service, a faulty stator can damage the power pack as well.


I havent been been able to get a DVA yet. However I disconnected the the wires That it says to in the link above on the stator. I also disconnected the two yellow stator wires at the terminal block .Here's the resistances I got.

white to blue 28.2ohms
white to green 28.0ohms
brown to brown/yellow 0.834kohms
orange to orange/black .411kohms

so the orange to orange/black resistance is out of spec? Is this because I only disconnected the wires and not removed the entire stator? Could the resistance be different because the stator itself is grounded at the engine block?
 
The tach works off of the yellow- brown/yellow wires. Is there a tar like goo dripping off of the stator? If so the stator needs replaced and is recommended to replace the rect/reg at the same time. Do not use a maint free or gel type battery. It is also recommended to run a high amp draw appliance when running WOT to use the excess power produced.
 
I ordered a voltage regulator rectifier on eBay, guy said it was pretty much new he installed it on the boat for a couple hours and took it off. I'm guessing that wasn't his problem.
Anyways I ordered the voltage regulator rectifier from him and I installed it and now my tach works again. I did order a DVA just in case anything else happens down the road I'll have it and not have to wait for shipping.
Took the boat out yesterday and my battery voltage only read 11.9v with the motor off and 12.9 with it at WOT. I'm thinking my battery was just pretty much drained.

Thank you you everyone for the help it was very much appreciated
 
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