evinrude 50 overheat alarm

[tylerr83]

The overheat alarm on my 87 50 has beein coming on after a idling for anywhere from 5-10 minutes....the entire water pump assembly has been replaced as well as the thermostat...dropped the lower unit a second time to make sure the impeller was in properly, and everything aligned right (water line and so forth)....the alarm still goes off...
i'm not sure where to go from here...but heres some more info
1. good stream from the telltale (in the water, not just with the muffs on)
2. water from tell tale is cool to lukewarm
3. can put my hand on the flat part of the head for 3 seconds or so before its too hot
4. i did notice one small hole in the water line which is copper...but it looks like its supposed to be there...its not corroded or anything and is perfectly round

i've read that the thermostat should open at 140...so it should run around 145 or so....and the temp sensor should trigger the overheat alarm at something like 200-212....
i know that i would not be able to touch anything at that temperature....this info was also told to me by a tech today at a local outboard place the tech also said if i brought hte motor in right away i still wouldn't get it back tidll may because they are so backed up this time of year, so i'd like to correct the problem myself if i can
i dont know where to go from here....my next step would be to replace the temp sensor...other than that the only thing i could think of would be some blockage in the powerhead...maybe an issue with a deflector....
any info you guys can give me would be greatly appreciated...
thanks,
Tyler

 

[tashasdaddy]

Re: evinrude 50 overheat alarm

check for a short in the sensor wire, the sensor grounds the circuit, to sound the horn.

 

[tylerr83]

Re: evinrude 50 overheat alarm

i can find any short in that wire...when i first started dealing with this problem i did disconnect and ground those wires to the head and it sounded the alarm...am i reaching to think that theres a problem with the sensor itself...part of me feels like i am....while i have the cover plate off i'm tempted to pull the head off to see if theres some blockage behind there where the deflectors are...i'd hate to have to do this again after putting everything back together for the second time
are these plausible options?

 

[HighTrim]

Re: evinrude 50 overheat alarm

You could test your temp sensor as per your manual to rule that out. You also need to determine if in fact you are overheating. Do you have access to an infrared thermometer? When the water pump was replaced, did you flush the water line to and from the t stat housing to ensure proper water flow? I also beleive there is a small hole at the t stat housing that must be clear of debris.

 

[tylerr83]

Re: evinrude 50 overheat alarm

when i replaced the thermostat i did flush everything out and there didn't seem to be any restriction in water flow...i would like to test the sensor per manual instructions...however i bought the motor without that manual...just recently ordered one from kencook.com, but i dont know when i'll actually recieve it...i've been considering an infared thermometer....would i be able to use any other type of thermometer to determine the temp at idle....i know that it might not give a dead on reading because of heat transfer, but it would be close right?

 

[tylerr83]

Re: evinrude 50 overheat alarm

ordered a new temp sensor/sending unit...should be in tomorrow...hopefully this will take care of the problem...i really dont think the motor is running hot...it is without a doubt cooler than it was before the water pump/thermostat replacement...gonna see if this does the trick...

 

[Boatbum11]

Re: evinrude 50 overheat alarm

ordered a new temp sensor/sending unit...should be in tomorrow...hopefully this will take care of the problem...i really dont think the motor is running hot...it is without a doubt cooler than it was before the water pump/thermostat replacement...gonna see if this does the trick...

Do you recall if that did that do the trick? How did you remove the temperature sensor? Did it have the rubber seal keeping it in place? If so, how did you pop that out?

 

[Crosbyman]

topic is 14 years old !!! best to start a new topic

 

[Belfast Bill]

I'm having overheating problems with my VRO 70HP 1993, I have taken the thermostat out to check it,she's pumping through the pee hole great but over heated while testing yesterday in the dock and stopped. When she cooled down I took the thermostat out and started her and it was pumping up to the thermostat housing and out the back, put the housing cover back on without the stat and she ran smoothly.

 

[racerone]

Does the hose and tell tale fitting come off the side of the block ( 1993 70 HP ) or the top of the block.-----There was a service bulletin in 1994 to move it.-----The latest water pump kit has the instruction and parts for cooling issues.-----Also do a compression test and post your numbers.----They will close this thread so start a new one on this 70 HP.