Johnson 115hp 2001 tach/system check problem

[JennySweden]

Hi,

I have a small boat with a Johnson 115hp on it. Recently two problems has appeared, dont know if they are related or not....

First one: The 4 warning lights in the tach does random self tests (like they do when I turn the ignition on) when the motor is running. The tach itself seems to work ok, the problem only affects the warning lights.

Second problem: When we start the engine and take off it sometimes doesnt rev over 2500 rpm, I suppose it goes into slow mode for some reason. It does not rev over 2500 no matter how many tries we make... But if we turn it off with the key and starts it again it always works as normal. No warning lights are litten but that might be because of problem #1.

Could someone please help??

(Im only translation for my BF, and please excuse my bad english =))

Kind regards,
Jenny

 

[Chris1956]

Re: Johnson 115hp 2001 tach/system check problem

Jenny, The symptoms may or may not be related. The System Check Gauge will self chack everytime power is applies. I have a loose wire on my boat and the Tach self-checks every time I hit a decent wave. The Tach is unaffected. I simply cannot find the loose wire.

As for the low RPM, try disconnecting the overheat sensor where it connects ot the power pack and see if that helps. Of course, you will need to make sure you are not overheating. You might test the thermostats and change the waterpump impeller for safety.

 

[JennySweden]

Re: Johnson 115hp 2001 tach/system check problem

Hi

Ok we have tried and cannot measure any voltage drops while the motor is running.

Can the motor go into slow mode because of the tach? Or is it only one way comm?

Ive read other posts regarding similar problems and we might think that there is a problem with the horn device, or maybe the blocking diod.

Our dealer want to sell us a new tach, but we've tried it out of the boat with just 12v and its works fine... Cant get the output for the horn to connect to ground though when we simulate an alarm... But since alarms only trigs the horn when the motor is running it maybe needs a rpm signal??

Kind regards
Jenny

 

[Randyg123]

Re: Johnson 115hp 2001 tach/system check problem

Jenny, The symptoms may or may not be related. The System Check Gauge will self chack everytime power is applies. I have a loose wire on my boat and the Tach self-checks every time I hit a decent wave. The Tach is unaffected. I simply cannot find the loose wire.

As for the low RPM, try disconnecting the overheat sensor where it connects ot the power pack and see if that helps. Of course, you will need to make sure you are not overheating. You might test the thermostats and change the waterpump impeller for safety.

Jenny,

Hej
I agree with Chris1956. I had a depth finder that would re-start on me when moving at high speed. Turned out to be a loose connection on the ground wire. If watching the voltage on a Digital Multimeter while moving across the water, a sudden drop in voltage may not be noticed by the meter but still trigger the tach to re-start.

I don't see how the tach could affect your rpm or trigger the slow speed but if you really suspect the tach, just disconnect it and take the boat out to see if the rpm issue still exists. I don't think you need a tach to determine the motor will not exceed 2500 rpm, that will be obvious.