heat alarm

[jig]

I have a 1985 60 hp johnson that the heat alarm goes off with in 5 mins. after I start up.The motor dosen't seem to be overheating and after I turn it off and wait a few mins. and restart it runs fine. I replaced the water pump about a year ago.Does anybody have a idea what the problem is?

 

[Frankies Marine]

Re: heat alarm

Check the over heat swicth on the head, should be a brown single wire coming from the head, next time the hore goes off, unhook this wire see if horn quits, if so the motor is overheating or bad switch, let me know if needs parts or i can be of help, Thanks Frankie<br />Frankies Marine<br />918-786-8180

 

[stein86744]

Re: heat alarm

I have a 1987 70hp Johnson. Recently an alarm has been going off sporadically i.e occasionally when I start the boat and also when running the engine for awhile. The alarm sometimes stays on indefinitely, and sometimes shuts off after a minute or so. Also, if I shut the boat off and start it up again the alarm often does not come back on for a bit?? Is this a known issue? Do I check the sending unit? Wiring of the alarm? Oil pressure? Cooling system? Thanks!!

 

[oldsalt]

Re: heat alarm

stein86744 I too am having this intermittent problem with the warning horn. After reading your reply and the leading notes I feel that the problem is with the heat sensor itself. I have a 1992 60HP Johnson so the problem has been around for some time. Did you manage to fix your problem. <br /><br /><br /><br />------------------<br />Still waters and tight lines<br /><br />Oldsalt

 

[Big Rod]

Re: heat alarm

OK captains,here's the way the overheat sensor is wired: The horn is permanently wired to a positive (+) connection and always looking for a place to complete it's circuit through a ground. The overheat sensor is a switch that creates that ground when an overheat condition exists. Unfortunately,the same wire that goes to the heat sensor (tan) from the horn can sometimes become frayed and allow the horn to find that ground through that frayed tan wire and sound off. Most of the time the system is doing it's job.You can sometimes get back to the landing with a sounding horn if you idle down. However, if water is poured (by hand) over the powerhead and a sizzling sound is heard and seen, shut it off quickly or it will shut itself off for you (crater).

 

[oldsalt]

Re: heat alarm

Thanks for the quick reply Big Rod you have given me another avenue to explore as I now find that the alarm sounds even if I disconnect the sensor. Now, without sounding too much like the outboard tech newbie I am, can you clarify something else related to this problem. I get this continual horn warning as soon as I turn the ignition key to the 'On' position and it stays on until I turn it off. It continues whether the motor is running or not so I don't think I really do have a heat related problem but probably a wiring one. This morning I started poking about inside the wiring harness itself and found this wire pathway starting from the sensor. A short tan wire with a blue stripe leads from the sensor to the first plug next to the top cylinder where it connects to a tan wire. This wire then pops into the harness and comes out just beside the fuel filter where there is another plug with a bright green wire leading down under the power head and into oblivion. I used my multimeter to verify the pathway. Can you tell me the most likely spot where this wire could be frayed as I am most reluctant to start dimantelling the motor to find it. Thanks for your help and I am really glad I found this forum.<br /><br />------------------<br />Still waters and tight lines<br /><br />Oldsalt

 

[Big Rod]

Re: heat alarm

Old salt, sorry, I responded again and was rather lenghty and it got lost as soon as I hit the submit button. I am out of time now...

 

[oldsalt]

Re: heat alarm

I thank you Big Rod for all your replies and I know how it feels to have a lengthy technical explanation eaten by one program or another. All of the wiring from the consol control back to the motor are encassed in waterproof sheathing and seem(??) to be intact with no visible breaks or wear points so I think I will concentrate on that portion of the line that is in the motor itself. I had the power head replaced two years ago with a factory sealed unit so that may be the cause of the wear on the insulation. I will be working on it later today as Muskie season opens on Saturday in this area and I can hear them calling me now. Cheers.<br /><br />------------------<br />Still waters and tight lines<br /><br />Oldsalt

 

[stein86744]

Re: heat alarm

Alright, nearly two years since my last post to this thread, but the problem has been more constant and I finally investigated it and had a few more questions.<br /><br />Recap: I have a 1987 70hp Johnson, the overheat (constant) alarm sounds at random times (sometimes after a minute of running, sometimes after an hour). Engine is cool to the touch so its not sounding for a real overheat issue.<br /><br />While alarm was sounding I unhooked the knife connector (tan wire) for the heat sensor and the alarm stayed on (conclusion: the heat sensor is not the problem).<br /><br />I checked for a fray in the wire that might be grounding out, but did not locate any issues.<br /><br />I took apart the handset / throttle assembly and disconnected the tan wire from the alarm assembly (small 1 inch box in handset) while the alarm was sounding and the alarm still stayed on. Conclusion: the alarm is a problem itself, perhaps shorting/grounding out within the alarm??? <br /><br />The only other thing I can imagine, but which seems unlikely is that the purple (VRO?) wires coming into the alarm are creating a ground for some reason, but the alarm is giving me the constant overheat alarm incorrectly?? I did not pull the purple wires off of the alarm assembly while the alarm was sounding to test this.<br /><br />Based on the above info, thoughts on how to correct my issue? Also, if I need to order the alarm assembly where should I head to (website) or call for this Johnson part? Thanks in advance!!!

 

[seahorse5]

Re: heat alarm

The purple wire comes from the key switch and supplies 12 volts to activate the horn. If the horn still sounds after disconnecting the tan wire, which completes a ground circuit thru the temp sensor or VRO circuits, then you have an internally shorted horn. The new replacement may be shaped differently and has an extra ground wire attached to it. It also gives off one beep as a self test when you first turn the key switch to ON.

 

[DJ]

Re: heat alarm

stein86744,<br /><br />When is the last time you cleaned out your VRO tank?

 

[OBJ]

Re: heat alarm

Stein....let me build a little on what djohns posted.....find the leads from the VRO tank under the motor cover. It will look like a black lamp cord. One side will go to ground and the other will problably be a "bullet" connector. Disconnect the bullet connector and see if the horn sounds. If it does, clean the VRO oil tank out and try again. If the horn sounds again after cleaning, replace the Unit in the tank.

 

[stein86744]

Re: heat alarm

Thanks for the help. Quick clarification: Seahorse mentioned that if the alarm continues to sound after I remove the tan wire (and it does) then my alarm is internally shorting.<br /><br />But the next posts begin to direct me toward investigating my VRO? The alarm I get is continuous (not oil?) and once I remove the tan wire the alarm continues (internal short?). Therefore, could this still be my VRO?<br /><br />By the way, where can I order the part?<br />Alarm Part Number: 583891, 07-I-R, Mexico

 

[clanton]

Re: heat alarm

The 92 model has service bulletins for overheat, overcooling, and cooking the middle cylinder. You should be able to find the by searching this board. The Oem waterpump is an upgraded pump with 2 addition changes to the cooling system. The early self test warning horns were junk. Check the wires for shorts to ground, then replace the warning horn with fresh horn, not from old stock.

 

[seahorse5]

Re: heat alarm

If the horn still sounds after you disconnect the tan wire, then unplug the "VRO" wiring at the pump, if the horn still is blowing, disconnect the wires from the oil tank where they connect at the motor. The oil tank pickup can give all kinds of wierd horn sounds if it goes bad.<br /><br />If the horn still sounds, then it is shorted, or there is a short to ground somewhere in the tan wire inside the wiring harness, control box, or under the dash.