Actually this one is probably the correct one: https://www.cpperformance.com/p-1307...si-gauges.aspx

Not sure what the OP is running but on my engs, on the thermostat housing, there's a temp switch and a temp sender. They look very similar and the connection is the same type (ring terminal on a post with a nut). The temp switch actuates the warn horn if temp gets to high.

This whole thing started because of the engines inability to build any heat in the oil or water despite having thermostats in both systems (water has a crossover with bypass and stat which I know some people dislike because of these problems, but I'm trying to learn exactly why some work and some don't before abandoning the setup). I initially thought it would just be a matter of selecting the correct t-stat to get some water temp, so I went out with 3 different stats to get some temp readings and couldn't get the gauge to even move. The gauge starts at 100° so I was either under 100 or there was a gauge / sender problem. Just for the hell of it I decided to run without the t-stat to see what would happen. In the few minutes it took to get the boat on plane and trimmed out the temp gauge was at 200°. I could tell by touching the engine that it was definitely hotter but this seems a bit extreme to go from <100 with a stat to >200 without one in a couple mins. This is why I was looking to rule out the sender as a problem. After going out again today with a temp probe I'm inclined to believe the sender is correct and those are the actual temps.
-
- if anyone has any thoughts on why I can only get 80° with a stat but hit 200° without one and nothing in between I'd like to know.
-
As far as the sending units go, it would still be nice to figure out exactly what the correct one is for this type gauge in a non marine application so it can be purchased locally and not have to go mail order through CP.
-
Griff, all the electric gauges say Gaffrig Precision Instruments. All the mechanical gauges just say Gaffrig which I thought was interesting that they were labeled differently.

Sorry about the terrible photo but battery was too low for flash so i had to try shining a flashlight on it.


This is the t-stat housing which has a diverter in it so bypass water doesn't go right on the thermostat. In theory...

What if there is not such a thing ? If I was having a problem I would want to make sure I had the correct sending unit. You would have already had it by now if you ordered it from CP.

I ruled out the sending unit last time out by using a separate device to read temps. My gauge readings are correct, I'm under 90° with a stat and at 200° very quickly without one. I didnt want to order one from CP because yesterday was the last run for the year to burn the fuel out of the boat for the winter so I figured I'd use it to do some testing as the boat was only out a few times all year and even in the warmer temps it wasn't building heat but I just didnt have the opportunity to look into it. I was looking to get a sender in the morning and use it the same day thinking that would be easier than opening hatches and manually checking temps multiple times. I don't believe Gaffrig developed a proprietary sender just to use in their gauges but of course I might be wrong.

Those are similar to my gauges, except the position of the numbers. Mine use a stock Merc sender. If you look at mine, you will see my 165* position is the same as your 200* location. So, yes I do think you probably have the wrong sender for your gauge. If you pull the gauge it should have a sticker on the side that tells you what ohm sender it needs.

If you go to the Industrial Series gauges, the 100-250* gauge has the same layout as yours and it should use the same sender. http://www.livorsi.com/pdf/lmi%20volume%2018_rev5.pdf

I'll pull the gauge and see if I can find the sticker you mention. Thanks for the info.

When I wanted to verify temps I`d boil some water on the stove let it cool a bit , put in a $5 thermometer and the sender and see if they read the same