2000 Johnson 115 running a bit warm

[bullgator99]

My Johnson 115 ran all last year around 140 degrees. When I started using it this year, I noticed the temp ran up to 160-165 degrees.<br /><br />The temp runs highest when I'm lugging along at low speed. If I give it more throttle, the boat comes up on plane (around 3200 rpm) and the temp quickly comes down.<br /><br />I thought it might be the water pump, so I changed that. I fired it up today and the temp still goes up to 165.<br /><br />I took a look at the thermostats today. There were some tiny pieces of gravel inside the engine. The thermostats looked okay so I put them back in.<br /><br />What do I do next?

 

[OBJ]

Re: 2000 Johnson 115 running a bit warm

Which side was running hot? One head can heat up and the other not if the t-stat fails closed on the hot head.<br /><br />You really need to test the t-stat to make sure they open at the specified temp. You can't really tell that by just looking at them.

 

[bullgator99]

Re: 2000 Johnson 115 running a bit warm

Thanks for the reply.<br /><br />As a matter of fact, I took the cover off just after running it and I noticed the starboard head was a lot warmer than the port head.<br /><br />What's the best way to test the thermostats?

 

[DHPMARINE]

Re: 2000 Johnson 115 running a bit warm

The starboard head will generally run WARMER than the portside head.Something you can notice with your hand ,but not alarmingly so.<br /><br />Testing the thermostats maybe a good idea to pinpoint the problem,but when 6 years old I just replace them.They maybe opening erratically.<br /><br />The problem I see is you are now running 25 degrees above normal,and 163 degrees is considered overheated.You may be doing damage to the powerhead.<br /><br />I'd try some new thermostats.Also do the seats.<br /><br />DHP

 

[Solittle]

Re: 2000 Johnson 115 running a bit warm

You can teat them by putting them in a pan of water and heating on the stove with a thermometer. I would replace regardless.

 

[R.Johnson]

Re: 2000 Johnson 115 running a bit warm

Don't lug the engine at that speed. You are at the point the thermostats open, but not fast enough to push the poppet valves off their seat's. Run at that point long enough! you will have a problem. Increase the speed, and you will drive through that problem. You have found a problem point with your engine! Don't insist on staying there.