bigmacdaddy1967

[bigmacdaddy1967]

Ok I'm at the end of my rope. Help! I have a 1987 johnson 70 hp motor. The high temp alarm is going off at high rpms. I've replaced the water pump and the thermostat and both are working fine. But the high temp alarm is still going off. I took out the high tem senor and there is no alarm with out it but I don,t want torun it that way. I tested the sensor in a pan of oil and with a thermometor and the sensor is closing at 197 degrees and it opens back up at 163 degrees. Accordind to my generic manual it should close between 205 and 217 degrees so it is a little off. However its a generic manual! I can run the motor all day just below or at slight plain with out the alarm going off. Is it possible I have a flaky thermostatic switch? Help

 

[bob johnson]

Re: bigmacdaddy1967

you need to verify what the actual head temps are....

but it is possible the last few rpms are enough to create too much heat...

you may have clogged passages.

what the motor run in salt water during its lifeZ??

is it possibkle you sucked up some seaweed and or algae???

some of that stuff can get through the "screen" and get hung up some place


good luck

bob

 

[tashasdaddy]

Re: bigmacdaddy1967

get one of these and check head temps

http://www.harborfreight.com/infrared-thermometer-93984.html

 

[bigmacdaddy1967]

Re: bigmacdaddy1967

I place a digital thermometor in place of the temp sensor and the engine got up to 220 degrees. then I removed the thermostat and ran it full throtle again and it only got up to 172 degrees. I put the old themostat in and did the same and it got up to 205 degrees. The OEM substituted thermostat was not allowing enough water to flow. The old one is better but still a little on the hot side. I'm de scaling the old termostat now to see if it helps.

It was never ran in salt water.

1. is there a safe way to descale the engine coolant passages?

2. Is is 205 to 217 degrees the correct range the thermo sensor to activate the alarm my current sensor is 8 degrees below this range at 197 degrees?

 

[bob johnson]

Re: bigmacdaddy1967

Id think that over 200 is too high!!!!

some guys put dawn dish detergent in their garden hose and then install the muffs on the hose and put them on the motor, when they turn on the water and quickly start the motor , they are running the dawn through the block...and supposedly that helps disolve corrosion inside..

how are you insatlling a digital thermometer, in place of the sensor????

with an outboard motor sending unit???? and digital boat gauge???

I was getting 170-180 and a little higher temps and when i left the thermostatt out...the temps never went above 120!!!!!!!!!!!!!!

the t-stats sure close off flow even if they are working.....



bob

 

[bigmacdaddy1967]

Re: bigmacdaddy1967

I have a digital themostat meter with a bi metal wire sensor. I inserted the temp switch and then sensor wire and then use the ruber plug from the temp switch to hold the wire sensor in place. then I taped the display to the front of the motor so i could read it while I was driving the boat.

what about flush th block with white vinegar like a coffee pot?

 

[Pokertrampp]

Re: bigmacdaddy1967

You can buy some Temperature recorders and put one on each head (or anywhere you want to record the temp) and when you run the engine it will record the highest temperature the engine reaches. I have used them for over 15 years and have found them to be very accurate. The ones I use I purchase from Caterpillar, but I have seen similar ones for sale at local motorcycle shops. Here is a link to a place that I found online so you will know what I am referring to, if you don?t already know. You can buy them in several different temp ranges/increments. Hope this helps, Good Luck!

http://www.ktm-parts.com/mm5/merchant.mvc?Screen=PROD&Product_Code=43200427