87 Johnson 88 HP SPL Over Heating Update

[jerryny]

I did the following to try and fix the over heating problem I was having

1) Rebuilt water pump
2) Replaced both head gaskets and water deflectors
3) Cleaned out all water passages


Idled it for about 15 minutes and then took some readings using a infrared thermometer

Results:
All 4 cylinders were reading about 126 degrees. Temp Gauge read 140 degrees

Does this sound ok??

Thanks
Jerry

 

[emdsapmgr]

Re: 87 Johnson 88 HP SPL Over Heating Update

The thermostats on that engine open at 143 degrees. That engine will normally idle at that temp after 15 or 20 minutes. I'm suprised the laser gun is reading 126. Maybe try another gun?

 

[jerryny]

Re: 87 Johnson 88 HP SPL Over Heating Update

I ran it again for about 30 mins, the temp gauge on the dash was reading about 150 degrees and the infrared gun said 135-140. So you might right about the gun. I will try a new battery in the gun first and then if i get the same results I can try and borrow a gun.

How accurate is the dash temp gauge??

Of course the real test will be when I can get it in the water. I'm having hand surgery tomorrow and that will leave me unable to put in the water for 2 weeks. Hope they don't take the docks in before that.

Thanks

 

[Fed]

Re: 87 Johnson 88 HP SPL Over Heating Update

You can't trust an infra red gun for outright temperature because it will vary depending on the colour of the object being measured. (Google emissivity)
Good for a comparison test test though.

 

[emdsapmgr]

Re: 87 Johnson 88 HP SPL Over Heating Update

That engine will sound a hot horn at 212 degrees. Horn will silence at 175. That's still hot. Not unusual for an engine to idle in gear at 150 or 155 in a warm lake in mid summer.