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Author Topic:   Temp gage reading high at idle
Ray posted 08-14-2001 03:05 PM ET (US)   Profile for Ray   Send Email to Ray  
I need somebodys wisdom on this. My 1985 Johnson 225hp outboard runs hot on the temp gage at trolling speeds but ok at cruising speeds. My gage is the OMC green/red gage. at cruise the needle is always in the middle but when I slow down in the no wake zone it creeps up to the red line but not quite into the red. There is a hint of steam from the exhaust at slow speeds but not serious. I can lay my hand on the heads but not leave it there too long. The starboard head is slightly warmer than port. The engine was rebuilt 2 years ago and new water pump installed. It does pee a good stream at idle and at full throttle. Should I be concerned??? I've been thinking of installing a new impeller and new thermostats. Also, would idle timing cause some elevated temperature?
Thanks for any advice,
Bigshot posted 08-14-2001 03:32 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Sounds like impeller. Try that first. Let us know.
MikeC posted 08-14-2001 08:45 PM ET (US)     Profile for MikeC  Send Email to MikeC     
I would replace the impeller.I just replaced one in a 1999 115 Evinrude that you would swear was brand new but it was not cooling like it should.The one I pulled out looked like it just came out of the package.
Bigshot posted 08-15-2001 09:47 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ray if it looks good like Mike said, replace it. I would probably do the whole pump just to make sure. The vanes get "formed" and do not throw enough water. Follow the other post on how to do it.
Ray posted 08-15-2001 10:39 PM ET (US)     Profile for Ray  Send Email to Ray     
Thanks guys, I'll try it and let you know.
lhg posted 08-16-2001 09:29 PM ET (US)     Profile for lhg    
Your problem could also be a defective thermostat, not letting enough water circulate at the lower water pressure obtained while idling. That's my bet, because you are indicating the telltale is OK. I had same thing happen to me.
Ray posted 09-06-2001 11:10 PM ET (US)     Profile for Ray  Send Email to Ray     
I talked to the tech guy today that rebuilt the motor 2 years ago. He said:
1. He installed a new pump and thermostats when the power head was rebuilt.
2. It is not unusual for the big engines to run hotter at idle and at trolling speeds.
3. Take a handful of water and dump it on the head and if it doesn't boil off it is not overheated.
4. If it passes this test don't worry about it as it is perfectly ok.
So what do you guys think?
Clark Roberts posted 09-07-2001 07:44 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Ray, heed the thoughtful advice on this forum! We don't want you to toast that engine! Don't know if your gage reads cyl head temp or jacket water temp (cyl head temp is always higher than jacket water temp)
but you may have a gage problem. Clark.. Spruce Creek Navy
Hank posted 09-08-2001 01:04 AM ET (US)     Profile for Hank  Send Email to Hank     
I'm with Larry on this one. It sounds like a bad thermostat. Pressure relief valves open at higher speed and cool the heads. Had a similar situation on my 90 Evinrude.
Ray posted 09-08-2001 11:09 AM ET (US)     Profile for Ray  Send Email to Ray     
Toasting my engine is the last thing I want to do. The gage reads cyl. hd. temp. as the sensor is bolted on the head and makes contact with the outside of the cyl. head. What I'm wondering is do any of you folks find your temp gage creaping up after running in and then ilding up the channel?
Clark Roberts posted 09-08-2001 09:00 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Ray, yes I notice the temp gage "creeping" up after running at speed and then slowing to idle/slow speed... this, I believe to be normal and it takes a few minutes to cool down with the reduced flow of cooling water at the lower rpms. But, the temp should not go up to or near the alarm point. Here in Fla. the water temps are very high in summer and this is a common occurance (at least for me!). I change water pump impellers once a year whether it needs it or not... Clark... The Old Man and the Sea

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