Temperature Fluctuation

[StefanMoore]

Hello. We have a 01 Outback V. The engine was rebuilt a couple seasons ago and has been running weird since. Since the boat was rebuilt the engine temp will go up to about 190-200 and them go down to 155ish. It does this pretty rapidly and we have tried to replace the thermostat with an automotive and a marine thermostat. If we take the thermostat out and run the boat the boat will stay steady at a 145ish temp and never climb. Is this something that anyone has seen? We are working on trying to figure it out.

Thank you!!

[Stazi]

Your engine water pump might be going bad. Not the raw water pump.


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[StefanMoore]

Thank you much! We will give that a try next. We have been messing with it a bunch. Hopefully this will get it back running good!!

[DOCDRS]

I assume you have a new impeller, and the stat is a 160 degree. When is it 190 and when is it 155, and how long does it take to get it to 155 and what if you neutral rev it at 190?

[JHutch]

I am having a similar issue. Put a new thermostat in last year and now I am getting fluctuation. At idle I can get to 190 give it a little throttle and it will instantly drop and stay low. Sometimes it drops to like 120. I am wondering if I have sensor issue? As in its reading incorrectly? Before I changed this thing would never budge off of 160.

[zabooda]

Could be a partial blockage.of your intake hose. When moving the hydrostatic pressure is much higher than the raw water pump.

[james yarosz]

JHutch,did you ever figure this out,my 2003 outback is doing the exact same thing.Used to run about 170 all the time,now after thermostat change the temp moves around from 180 to 140.Doesn,t seem to be related to any certain speed or rpm.Boats feels like its running fine.

[Branden967]

JHutch,did you ever figure this out,my 2003 outback is doing the exact same thing.Used to run about 170 all the time,now after thermostat change the temp moves around from 180 to 140.Doesn,t seem to be related to any certain speed or rpm.Boats feels like its running fine.

Are you sure a 160 degree thermostat was put back in? If it’s not going above the 180 mark, was a 180 thermostat put in by mistake?

[james yarosz]

Im not sure if it was a 160 or a 180,the problem is the temp fluctuates from 140 to 180.It doesn,t hold steady at one temp like it used to.

[Fossenrf]

Did anyone figure this out? Having a similar issue with my 03 Outback LS.

[HFarr]

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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[zabooda]

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/sensor-solutions/insights/understanding-rtds.html

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

[Fossenrf]

Found my issue in the transmission cooler.30485

[Holdmybeer]

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

[HFarr]

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

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[Fossenrf]

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.

[Holdmybeer]

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

[Fossenrf]

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.

[james yarosz]

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.

[Fossenrf]

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?

[Fossenrf]

This fixed my issue, once warmed up the temp gauge stays steady at 160 now as it should.

[james yarosz]

Mine started with a thermostat that was stuck open.The boat ran about 130 degrees all the time.Replaced it with a new stat and now it fluctuates.I will check the trans cooler again.

[Fossenrf]

What I did was remove the hose that comes from the raw water entry point under the boat. There is a metal screen about an inch or so inside the transmission cooler, I was able to reach in with a finger and scrape everything out. Hope that helps.

[james yarosz]

Yes,I know the drill.I usually pull that hose every year when I winterize.I haven,t done it in a few years because we have only put a few hours on the boat.Grandkids are getting older now and are starting to use the boat more.Also that hose sucks to get off!

[Fossenrf]

I hear ya. I am at the opposite perspective, with 4 kids under 12 decided we were overdue for a boat. I got what I thought was a good deal but am quickly learning that maintenance is more than just changing fluids every year and that the boat wasn't as well cared for as I was led to believe. I bought the boat in May and have already replaced all fluids, spark plugs/caps, thermostat, impeller, steering cable, blower fan, bilge pump, and greased the rudder. Still trying to figure out how water is still getting into the bilge, a couple gauges that don't light up at night, and need to add a water strainer after this incident. Oh well, the kids don't care and have enjoyed the almost 40hrs we've already put on it this summer!

[Holdmybeer]

Check your prop shaft thru-hull seal. Mine was leaking until this year when I changed it.

Only other water would come from ballast bags leaking or kids in and out jumping off the back.

[Fossenrf]

Forgot I also repacked the shaft packing nut. Pretty sure my leak is from both mufflers. Since I am not sure their condition (I’ve heard they can be brittle?) I am going to wait until the end of the season before I pull them out and see if I can patch them.

[james yarosz]

I bought my 2003 Outback LS brand new so I know its been treated well. When I first bought it both mufflers were cracked from someone over tightening the clamps on the inlet side of the mufflers. They were replaced under warranty.