johnson 140 hp temp

[tblshur]

i have j140tlcte , 83 model boat runs pretty good, got one of those hf infred guns and was checking temp .if 1 & 3 starboard and 2 &4 port then 1 2 3 seems to be 90 to110 and 4 will go to 125 f lake temp is 52 degrees could this be my enexperance with the tool or something else thank you for your help:joyous:

 

[emdsapmgr]

The laser gun should work just fine. Measure at the head, by the spark plug. The thermostats open at 143 degrees in normal summer water temps and may go up to 150-155 when idling at the dock. When you are on plane in the summer, the cyl head temps may run 20 degrees cooler. That's normal. If you are running in cold water-(as you are now,) and on plane (the pressure relief valves are open) the powerhead may only reach 100-110. Usually the heads will read approx. the same temps on both cyls on the same head, but can vary somewhat between heads. Am at a loss to explain the difference between 110 on 3 cyls and 125 on the 4th cyl. Suggest you let it idle in gear for a while, then recheck temps. That's when they you will see the highest readings. See what you get.

 

[Fed]

Those IR guns can give funny readings caused by emissivity, we used to go on heat seeking missions in the electrical industry and you'd be surprised at the incorrect readings. Wires recording the hottest values were often the coolest to the touch.
Make sure you are consistent in how you take the readings (angles) and all things are equal with the surfaces you are reading from.