Steaming Exhaust

[tugboat80]

I have a '92 15hp Johnson (J15RENM). I have had it for a week. It was preffering to run at higher speed to smooth out, and showed carbon in combustion chambers so I de-carbonized with Seafoam and DeepCreep. I added new L77j4 plugs gapped to .040, re-oriented the low speed needle adj and now have a smooth trolling motor to 1.5 mph as well as a smoother running motor throughout the rpm range and it tops out at 22 mph on my Hewescraft 14 Fisherman. But "the fly in the buttermilk is ..." (from Richard Boone in movie: The Alamo), It has started to emit steam from the exhaust tube. The tell tail flows good and the head does not feel over hot. Might I have coolant leaking thru the head gasket, or an impaired thermostat?

 

[Rick.]

Re: Steaming Exhaust

White smoke (actually vapor) is an indicator you have water in the cylinders. Steam is normally caused by an overheat. Plug gap is normally .030 . What did the old plugs look like? If one looked very clean that would also lead me to think you have water in a cylinder. Best of luck. Rick.

 

[Mas]

Re: Steaming Exhaust

I have a '92 15hp Johnson (J15RENM). It has started to emit steam from the exhaust tube. The tell tail flows good and the head does not feel over hot. Might I have coolant leaking thru the head gasket, or an impaired thermostat?

You may have a water leakage issue....pull the plugs...does either look really clean like it's been steam cleaned?

Also, do a compression check...possible head gasket if numbers are low or uneven...

Replace the impeller since you do not know when it was last changed

Or, what's the outside air temp while running?? Often when the air is cool, the motor looks like the motor has a water issue, but possibly only hot exhaust gases mixing with cooling water in the exhaust housing, then condensing in the cool air as it exits.

How many seconds can you hold your hand on the cylinder head when at temp? Two-three seconds is good!

Mas

 

[JSGOLD]

Re: Steaming Exhaust

My 8HP evinrude started steaming too....check your thermostat as well as the head gasket. My stat was on bad shape and the gasket was apparently leaking as well. Both plugs were clean (too clean) and the entire cooling system needs cleaned. Might as well do the stat, gasket, and pump to be sure everything is current and clean.

 

[tugboat80]

Re: Steaming Exhaust

I checked compression this AM, 7 strokes each: upper 111lbs, lower 120. Ran in water bbl with good tell tale, but no gurgle out the muffler. I pulled the t-stat, looked at it put it back in. Less steam than before, but lower head hotter than top. Lower too hot to touch for long.