Temperature Fluctuation

Does it fluctuate gradually over the course of several hours or is it actually moving up and down while you watch it.

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If it is an instantaneous change, it would be a bad connection. RTD sensors vary in resistance with temperature with 0 to 100 ohms. Wiring with good connections at 1 ohm is insignificant. A corroded or loose connection will cause the wire resistance to go up much higher and a large error. Instantaneous changes is a loose connection and a continuous out of range reading could be the RTD but more likely a corroded connection.


https://www.te.com/usa-en/industries...ding-rtds.html

A major cause of error can be the resistance of the lead wires, especially in two lead configurations.

Found my issue in the transmission cooler.Attachment 30485

Boat ok?
I'm hoping you didn't "find it" the hard way and now the season is gone.

Looks like spinach. If your temp never went above 200, you are fine.

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Temp gauge never went above 200, but I think the engine went into "limp mode" a couple times and would not let me accelerate until the temp came back down. Anything I should be worried there? It is going back in the water tonight to confirm that was the issue and that everything runs ok now. I also have already ordered the indmar strainer pro to make sure this doesn't happen again.

200 doesn't worry me. The lake water never enters the engine if you are closed loop cooling. The heat exchanger would be the gathering point. However, I thought the water pulled through the v-drive and Trans first so that makes sense that is where you found the clog. If anything I was worried about the transmission getting too hot. But most can handle way more than 200

I don't have a v-drive, just a direct drive outback ls. Transmission is the only thing I am really worried about since temp gauge comes from the engine, but agree it should be fine.

Realy like to know if that fixes your problem.The lake i,m on is pretty weedy and ever year when I winterize I clean some weed out of the trans cooler,but its never made the temp fluctuate until I installed a new thermostat.

I'll let you know hopefully tonight. Are you saying you started having the issue after you replaced the thermostat? Or that replacing the thermostat fixed the issue for you?