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Hi There I have a 97 model 25hp 2 cyl Johnson. Recently It has has been running fine for about 10 minutes and then goes into this limp mode and runs rough and shakes like its missing. It still idles fine and only runs at low revs. The telltale stream is very strong and the water coming out the water port -exhaust on the back of the leg is very warm . Could it be a faulty temp sensor in the head putting it into slow mode . or could it be an ignition fault . What should the temps of the water coming out of the exhaust and telltale be. Where should I start looking Could I have a blockage . Any help would be greatly appreciated as its been a great motor.
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If water from tell-tale is to hot to keep hand in, then motor is too hot.
If tell tale not too hot, carefully check different areas of cylinder head(s), if too hot to keep hand on (lower, middle and top- nearest sensor), then sensor is protecting motor from over heating. Is good chance blockage is preventing motor from cooling properly. Best option, try to flush motor with corrosion flush, vinegar, salt away, or anything good for salt corrosion & safe for aluminum. Should flush for couple hours in barrel/container large enough, to run motor continuously. If water in barrel gets too hot it may set alarm off, then let it cool for couple hours, then run again till water gets hot again and let it cool again.
If after a good couple hours of flushing it hasn't cleared the blockage, then you might have to clean the water passages manually.
Good luck, let us know how it's going. -
johnson25
Funny you mention that . I had an old mechanic tell me a couple of years ago that he fixes a lot of outboard problems with salt away. He swears by it.. I forgot all about it. I am away working for 2 weeks but will be trying it as soon as I get home. Thanks for your help .I will keep you posted.Comment
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25hp overheating continues
I tried flushing and it did not work . I have taken the head plate cover off and found the thermostat very dirty witha lot of buildup on it. I will now change the thermostat to see if it fixes the problem. Next I will change the temp sensor. How on earth do you get the temp sensor out of that hole. Does it screw in or does it press in. Am I missing something . Thanks for the help, will keep you posted.Comment
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If you buy a new one, it will either have threads or a grommet that's held in place with a plate on top?
Think thermostat was the problem, but clean all passages, blow out with air if available.
Good luck. Post back and let us know.Comment
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