Will the head temp and water temp be the same? Why not use auto temp guage?

[carlcath]

I have a 150 Johnson 1993. Model J150GLETG I plan to install some sort of temp guage. It seemed to me this should be a straight forward task but reading the post from a "temperature" search in this forum it appears it is not so simple.

First off, auto guages are readily available locally, are less expensive, and seem to be durable. We have one local boat store that has few parts. Any reason an auto temp guage with a range from 100 to 280 degrees and sender would not work?

If I can find one that will screw into the NEP holes in each cylinder it should read the temp at the head, not the actual water temp. What should that temp be for normal operating speed of about 2700 rpm or so.

I have the Johnson manual but it does not seem to mention what normal temp is.

 

[rpastor]

Re: Will the head temp and water temp be the same? Why not use auto temp guage?

In the Powerhead chapter, there should be a section "Engine Temperature Check".

 

[Silvertip]

Re: Will the head temp and water temp be the same? Why not use auto temp guage?

If the sender resistance range is a match for the gauge it will work. However, auto gauges are not moisture resistant and it will turn to a pile of rust in a short time. A gauge with a scale that starts at 100 degrees will barely have the needle off the peg. 140 degrees is a rough operting temp. Ideally, you should look for a temp gauge that starts at 60 degrees. These are getting hard to come by but they are still available.