Johnson 115 overheat??

[Metallizer]

I have a 1996 Johnson 115 that appears to be overheating. Prior to removing from the water, the temp light and alarm would sound after 1 minute at idle. I have since replaced the water pump and removed, inspected and reinstalled the thermostats. (the thermostats were replaced last year..they still look new).<br /><br />After reassembling everything, the light and alarms still come on. The starboard head definately seems to be hotter than the port side. The water pump appears to be working...strong stream from the telltale. What's odd is the temp light stays on after I turn the key without cranking. In other words, it shows "hot" even before the engine has been run (and has sat overnight). I disconnected the (2) sensor wires, and the light still remains on.<br /><br />Is it safe to run this engine without thermostats? Why is the temp light on when the engine is ice-cold?<br /><br />Thanks in advance.

 

[ob]

Re: Johnson 115 overheat??

I wouldn't run without T/stats.They have a design function.Try disconnecting the VRO harness and see if the light goes off.Did you ever run above idle speed after you had a light and alarm?Your engine should be equipped with the s.l.o.w. system that limits rpms when an overheat is detected.What audible alarm were you getting?Steady tone?Rapid short tones?etc..

 

[Solittle]

Re: Johnson 115 overheat??

Get some temperature sticks or find someone who has a temperature gun that you point at the motor and it gives the temp. That will confirm whether or not you have a real temp problem.

 

[seahorse5]

Re: Johnson 115 overheat??

If the hot lite comes on with just the key in the ON position and the motor hasn't been run and the temp senders are disconnected, then you have a shorted tan wire in the boat or on the motor, or a bad gauge. Check for bent pins or corroded connection on the 6 pin Deutsch connector that has the tan wires in it.

 

[Metallizer]

Re: Johnson 115 overheat??

Winter is nearly over and this problem still exists. After several hours today reinvestigating, here is the status on our 1996 Johnson 115HP V4 90 degree:<br /><br />1) "Hot" light remains on even when engine has not run.<br /><br />2) We have inspected all wires within the engine compartment looking for breaks/shorts. Even checked continuity where appropriate. No findings. In other words, we could not locate tan wire shorts/grounding.<br /><br />3)We have also inspected wires within the console area. No breaks/shorts.<br /><br />4) We tested the rectifier...it passed.<br /><br />We are running out of areas to investigate. Could it be a faulty tach/system check gauge? Or, power pack issues? How about cross-talk with the VRO?<br /><br />Anyone have ideas??

 

[Solittle]

Re: Johnson 115 overheat??

Metalizee - Now is not the time to try anything and everything in troubleshooring. While I agree with ob that you should not run these motors without t-stats for long - at this point I would remove them and check the temp. If the temp is OK you either had them installed incorrectly or they are bad. Did you replace the temp relief valves?<br /><br />Replace the t-stats after you are done.<br /><br />Another possiblilty is the deflectors in the motor or general crud in the water passages (salt water motor??).

 

[Metallizer]

Re: Johnson 115 overheat??

SoLittle,<br /><br />Prior to winterizer, I inspected the T/Stats and reinstalled them. I had just replaced them 1 year ago, for preventative maint. purposes. I ran the engine with muffs and while using a digital thermeter, I could see the T/stats were working properly. The temp. never exceeded 140 degrees. After running for 20 minutes, I could even keep my fingers on each head without significant discomfort. HOwever, the "HOT" light stayed on the entire time. In other words, I don't believe the engine is really overheating.<br /><br />Now that the engine has been winterized for 6 months, when I turn the key to AUX. position, the "HOT" light comes on. It makes sense that there is a short somewhere, but I can't find one.<br /><br />Has anyone seen this situation before? What can I check next?

 

[OBJ]

Re: Johnson 115 overheat??

Metallizer...have you tried disconnecting the temp sensors one at a time to see if either one could be bad? There is one in each head.

 

[ob]

Re: Johnson 115 overheat??

I'm with OBJ on this one.Either got a chaffed wire grouding out or one or both of the temp sensors are defective.

 

[Metallizer]

Re: Johnson 115 overheat??

OB & OBJ,<br /><br />Thanks for the suggestions.<br /><br />The HOT light stays on, even when both sensors are unplugged.<br /><br />I am wondering if it is the gauge. When I unplug the 6 wire plug/harness that goes from the motor to the console. the HOT light is stays on. This is the plug that includes 4 tan wires.<br /><br />Does a gauge problem make sense?

 

[ob]

Re: Johnson 115 overheat??

With all of the wires connected ,do you get the short system check beep when you initially turn the ignition switch to the "on" position?I'm thinking perhaps the alarm module itself may be at fault.Seahorses'post on Sept.3 has got you headed in the right direction.Just a matter of isolating which tan wire lead may be grounding and completing the circuit that keeps the overtemp light on.

 

[OBJ]

Re: Johnson 115 overheat??

What ob said.....with the connector disconnected at the engine, that puts the fault up front or, again, in the module.<br /><br />EDIT: Might take a look at the harness' route from the engine to the gauge, may have contacted a sharp screw or something of that nature.

 

[Metallizer]

Re: Johnson 115 overheat??

OB, OBJ, Seahorse,<br /><br />Thank you all for your help. I purchased a new module, plugged it in and the problem is fixed. Should have tried this much sooner...cost me $145 but I missed many days on the water.<br /><br />Thanks once again. This site is great. <br /><br />Metallizer

 

[Richard Cavanagh]

Re: Johnson 115 overheat??

You do good work! Now...if you can learn how to fish...

 

[rbruce63]

Re: Johnson 115 overheat??

Use a Thermomelt Stik to check for overheating or a digital pyrometer to be on the safe side.