1978 johnson getting hot

[trev]

I have a 1978 Johnson 140hp that is getting hot.This just happened last week for the first time.I was trolling and into it for about 3 minutes when it happened.The impeller seemed to be putting out a good stream of water out the pee hole.I pulled off the thermostats out today and put them in hot water and the both opened.Could this still be a impeller problem?Thanks for any help in advance.

 

[Walker]

Re: 1978 johnson getting hot

When was the impellor last changed. A worn impellor will put out a pisser stream but maybe not pump enough water to keep engine temps down. Scale buildup in the water passages and even internal carbon buildup will hinder cooling.

 

[JB]

Re: 1978 johnson getting hot

Howdy, B2F.<br /><br />You didn't mention any other symptoms. How did the engine behave otherwise? Was the telltale stream hot?<br /><br />There are several things that can cause overheating even when a good telltale stream is flowing. A failing impeller is one of them.<br /><br />Run a compression check, decarbonize, then run another compression check.<br /><br />Double check ignition timing. Is the stator returning fully at low throttle settings? A stretched or broken return spring on the stator will cause exactly the symptoms you mention.<br /><br />Let us know what you find.

 

[WoodsJ]

Re: 1978 johnson getting hot

Born2fish,<br />I was dealing with a similar issue on an evinrude, The following is assuming that your impeller is working correctly, some things to look for. Is the motor used in salt water?<br />If so, there is probably build-up of salt in the heads, try a product such as salt-away to clean it up if this is your situation. It won't get it all but it sure improves things.<br />When you checked the thermostats did you use a thermometer to make sure they were opening at the right temps? They could be opening later than they should be. If they have not been changed in awhile it is cheap insurance to put in a new set.<br /><br />I read your latest post, If compression is low in one cylinder and your motor has not been decarbed in some time, it could be stuck rings, this would not be a bad place to start.