View Full Version : Water Temp Sensor Wiring

08-06-2013, 08:05 PM
I have a 97 205 with the TBI engine. It has been running fine since I bought it a few weeks ago. The temp has been steady at @ 143 degrees, but I have installed 2 different (and new) 160 T-stats. So, I was checking the connections to the sensor and it was loose. I went to tighten it and found that the threaded stud was rotating inside of the sensor body. So, I removed the entire sensor and have a new one on order.

Then I noticed another wire in the harness going to the sensor. It is pictured below and looks to have been cut at some time. Just wondering if any has seen this before. I'm not sure why there would be 2 wires unless one is for the "limp mode".
Anyone near their boat may be able to confirm what I have or don't have.

08-06-2013, 08:10 PM
Sorry, graphics added

08-06-2013, 10:24 PM
Used to be another sensor right behind triangle of stat housing. Did they move it? There should be another sensor I believe. Is the wire brown and have a black stripe?

08-07-2013, 10:09 AM
Thanks. I went ahead and ordered both sensors, assuming that I would find the other. The guys at Skidim were helpful, but could not tell me where it should be.

08-07-2013, 07:18 PM
Working on the stereo, I found the tan/black stripped wire cut near the water temp gauge in the cluster. I assume that someone wanted to bypass the water temp switch, which I don't like that thought.

08-08-2013, 03:56 PM
The solid brown wire is for the temperature gauge sending unit, the brown w/black stripe wire is for the warning light sending unit. If your dash doesn't have the "Over temp" light, that would explain why the wire was cut.

The sending unit (ECT) for the ECM is a two wire sensor (black and yellow wires). This sensor will be located on the block below the head, normally on the right side of the engine.

08-08-2013, 04:11 PM
If you start having problems restarting the engine after you shut it down for a few minutes, you may want to put the 142 degree thermostat back in and read this thread. Not all boats will have this issue. Just a heads up.


08-08-2013, 07:29 PM
So far, I haven't had any issues except for high revs. I am tracking the linkage and IAC for that issue, but not running it until I get the water temp sender.

I only have a "Check Engine" and "Trans Temp" light on my dash.

On the starboard side, I have a knock sensor on the block and I found the 2 wire ECT sensor. I ordered both, so I will replace both. Thanks for the input, it really helped.

08-10-2013, 03:26 PM
I got the sensors and put them in. The water temp now goes up to 160 and is parked. The boat is seeming to be running better, but I also cleaned the IAC.

Now, I just filled up the gas tank and the gauge is still showing 1/8-1/4 tank. On to the next issue to solve.

08-10-2013, 07:46 PM
New fuel sender... I think almost everyone here has replaced that.... www.isspro.com or do you have the sender that can have the magnets reglued.

04-15-2018, 03:26 PM
I know this is an old thread, but I have a 1996 Mastercraft Maristar 225VRS with the LT1 and after reading everything I could about the wiring, I did my own sleuthing and discovered that the temperature sender (for me, on the starboard side) is wired directly to dash temp gauge, and the temperature switch (on the port side) is wired directly via a tan wire with black stripe (that becomes a dark brown wire with white stripe in the dash wiring harness) to the "Check Engine" light on the dash.