Proper Head and tell tale temps?

[benjiboy]

I have a 1989 120 Evinrude VRO with drastically different head temps. The port side head is approx. 130* while the starboard side is 35+* higher at 165*-170*; this is measured directly between the cylinders on each head. Both t-stat housings are right around 130*...

My tell tale water temp was measured at a high of 108*; does any of this sound way off base?

 

[JonathanMJ]

Check the thermostats individually by boiling in water. The primary reason i have seen varying head temps is found at the fuel or ignition system. Always good to do a quick compression test. I would then highly recommend checking individual temps to see if one cylinder is running weak so you can focus on that carb or ignition system. Is this a new issue, and has it affected performance? --Jonathan

 

[benjiboy]

Thanks for the reply Jonathan. Compression tested at 150PSI on the port bank and 140PSI on this much hotter starboard bank. Both thermostats were just replaced with the newer (black) style.

This boat sat for a couple years and I'm trying to get it water ready again; it idles well on muffs and in a tank but I haven't yet put it in the water yet. I am fighting heavy smoke, even after it is fully warm, and these varying heat temps. The tip of the bottom starboard spark plug electrode looked funny after this 30 minute idle....I have never seen one turn black at the tip like this.

 

[JonathanMJ]

Lots of smoke is normal when you first start up. Any fogging oil and residual two stroke oil will take a bit to burn out. Sounds like the starboard side is perhaps running lean. Have you run any seafoam in this motor? May fix it without pulling carbs. I generally shy away from muffs aside from cleanout because my old johnyrudes have their primary water intake above the skeg and just a couple small holes on the side inlet. May be different on a 120. Keep an eye on that plug and see if it gets any worse. Did the old spark plug look similar?

 

[Faztbullet]

These heads run hotter than the t-stat as the water valve allows very little water thru the head at idle.

 

[benjiboy]

This motor idled for 30+ minutes (in a tank, not on muffs) so I would assume any fogging oil would have burned off by now. The old plugs did not have this problem that I can recall but I do know this motor didn't smoke near this bad before its 2 year sit. I haven't tried seafoam but it will be on the list when I get time to wrench.

With this hot head, strange plug and major smoke I'm definitely thinking something is going on with that cylinder.

(as a side note, when I changed out the tstats before this most recent startup, I noticed the starboard tstat was a bit clogged compared to the port and I originally thought that was the cause of the head being so much hotter)

I want to get out on the water and put the motor under load but am embarrassed to start this thing on the ramp!

 

[JonathanMJ]

Find a 50's johnson to start it next to. My smokes more than anybody else's when it's been sitting. What color is the smoke? Does it smell like two stroke or like steam? It may have had a vro leak or just some old fuel that evaporated and left oil. My Johnsons are all grumpy if i haven't woke them up in a while. I'd try and get it in the water where i could turn a few rpms to see where you are at. (My barrel becomes empty very quickly if I get friendly with my throttle.)
Any other symptoms/memories of yesteryear that could help in the diagnosis?

 

[benjiboy]

I'll try to get this video uploaded...it's heavy and white but doesn't have much of a smell that I recall. I thought if there was any oil lingering it would have burned off after a 30 min idle.


It sat for two years (RIP Dad) and did not have this heavy smoke when it was running a couple years ago. The plugs that came out of the motor from two years ago all looked 'normal' and uniform so I want to say this is a recent phenomenon.

 

[benjiboy]

These heads run hotter than the t-stat as the water valve allows very little water thru the head at idle.

Is it common to have one head run at such a different temp than the other?

 

[benjiboy]

Got the video up. No mosquitoes around these parts!

 

[benjiboy]

Bump for more advise on the heavy white smoke in the video?

 

[benjiboy]

UPDATE:

Pulled the airbox off and found an excessive amount of pure 2-stroke oil probably a result of overpriming the oil line when the VRO was hooked up. Cleaned that up, changed the plugs from NGK to Champion, and replaced the plug wires which drastically reduced the smoke. Motor runs much smoother now, however, the starboard head is still much hotter than the port.