thermostat question???

[rook]

I can't seem to get my 78' 55hp Johnson to idle for nothin'. Would a malfuntioning thermostat cause this problem? The engine never seems to really warm up. How can I check whether it is working or not and is it difficult to replace?<br /><br />Thanks alot <br /><br />Sean

 

[steviecops]

Re: thermostat question???

Hi<br />I replaced the thermostat on my 1980 Johnson 55 recently. I knew my stat was either stuck open or missing altogether because I could rest my hand on top of the head for as long as I wanted and it only ever got warm. With the new stat I can now only keep my fingers on the top of the head for a second or so, but the motor idles better than before.<br /><br />Changing the thermostat was easy, but I had a head cover bolt snap on me which made the job longer than it should have been.<br /><br />While you're changing the stat, replace the pressure relief valve grommet also. My one had corrosion built up between the grommet and the head which made the valve a tight fit and stopped it from working properly. Both the stat and the pressure relief valve need to work together.<br /><br />I hope this helps.<br /><br />Good luck<br />Steve

 

[DHPMARINE]

Re: thermostat question???

Your motor should be running warmer,but this will not cause a no idle problem.I would suspect the carbs need rebuilding.<br />DHP

 

[rook]

Re: thermostat question???

Just rebuilt the carbs today , helped a little, but the engine does not heat up, just gets warm after idling at mid range rpm's for about 1/2 hr in a bucket, does not warm up at all with muffs??? Once the engine warmed up a little bit it did idle better, but no where near perfect. I've changed ignition coils and plugs, syncronized according to the manual, and decarbed the hell out of it. It does run better but still not good enough, and I'm not that picky, it can spit and sputter as long as it stays runnin', but it won't. It runs good past low speed idle. I'll try changing the stat but is there anything else I could check?

 

[OBJ]

Re: thermostat question???

sgd....at idle, the engine should warm up to the point that you can lay your fingers on the flat area on top of the block just forward of the heads, for several seconds before having to pull them away. A cold engine is not good for a smooth idle. If the engine is not warming up but is pumping water good, it is usually the t-stat that is at fault. You need to get the engine up to norm temp.

 

[steviecops]

Re: thermostat question???

sgd<br />I did all the things you have done, and some more to try to get my 55 running smoother at idle.<br /><br />I also replaced all the fuel lines, cleaned all the ground conections on the engine, rebuilt fuel pump, etc.<br /><br />I think the stat will make a difference in your case because my engine will still idle rough and die if I put it in gear just after cold starting, but after it's warmed up for a minute or two it is fine and will idle in gear with no problem.