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02 DF70 random oveheating

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Redden3056

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A couple weeks ago I made a WOT run to a spot that was about 30 mins away. I was idling in the channel due to it being shallow. My motor dies and I thought maybe I’d bumped the bottom. I go to restart and my battery is dead. So I swap to a trolling battery and make a u turn back to the ramp. My voltage regulator had died. So while I’m at it, I’ll go ahead and do some maintenance with torn down. I order the regulator, new impeller, oil, filters, ect. I get everything done and head to the lake. I idle away from the ramp and about 30 seconds at WOT, it alarms for overheating. I had a good stream at the tattletale. I eased around for the next few hrs. Long as I kept it under 5,000 RPM, no issues. Soon as I go WOT, it does again. I get home and drop the lower unit to check my pump. That’s fine. I pulled the thermostat and poppet. Seem fine, but I did not actually test the thermostat. I have order new ones, but until they come in, has anyone else experienced this? Is my inexpensive impeller from Amazon the culprit? It seemed ok. It’s just strange how I’ve had zero issues with this engine and now this. Thanks
 
Forgot to add that yesterday I spent all day fishing several spots. WOT runs back and forth with no issues. Then when I went to leave for the day, it started doing it again. I stayed around 4800 RPM and it didn’t do it
 
I personally wouldn’t depend on an Amazon impeller. It might not be the cause of your overheating issue but if it wasn’t overheating before the new impeller then it’s probably the Amazon impeller.
 
My old wasn’t terrible looking really. I only have around 300 hrs on the motor and it’s been several years since I changed it. I’m gonna order a OEM one.
 
So I may have figured this out. I’ve ordered a new thermostat and poppet. They should arrive today in the mail, so I went ahead and removed the old ones this morning. My old thermostat is stuck OPEN. I had to force it by hand to close. I threw it in a pot of water and it did open at temp, but seemed to not smoothly do so. Once it cooled it stayed open again. So either it was not maybe opening fast enough and I would get an overheat alarm, or maybe it was open all the time and I was hot spotting due to being so? Like I mentioned, it only would “overheat” at WOT. As long as I stayed under 4500-5000 RPM, no issues. I guess we’ll see once I get the new one installed.

So to reevaluate, I had two separate issues happen basically around the same time. The voltage regulator going out and the thermostat causing issues. When it rains, it pours.
 
Ok. So I replaced the poppet and the thermostat. When I opened the thermostat housing to replace, the old one was stuck OPEN. I tapped on it and it closed. Well maybe that’s my problem. I installed new thermostat and head to the lake. It done fine for several hrs of rushing spot to spot. Then when I went to leave for the day, about 10 mins of heading to the ramp at WOT, it did it again. So I get home and tear the bottom back off. Looking at the wear plate on the Amazon impeller, it looks like it isn’t making full contact. It isn’t a solid, circle wear pattern, but just a circle where the outside of the impeller is the only part making good contact. I have a new OEM kit coming. This has been so frustrating…
 
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