Carbon Blowout?

[Paulywog0667]

I've been working on an old 1972 hydro-electric 50hp. New powerpack, coils, reg/rectifier, rebuilt carbs, seal kits and lower gear assembly.

Was running great while tuning. Water was circulating out the back, but I see what looked a heavy oil smoke give a puff of black and noticed black from the block area holding the thermostat. The water turned a carbon black. Not the type C oil color. I didn't have the alarm hooked up. The plug wire plastic melting gave way to making itself a kill switch against the power head. It got hot, but after a couple hours, it kicks over with choke.

Does it seem like the thermostat froze shut and its gasket blew out? I'm concerned what other rubber is in that area? I did order a thermostat and gasket. Water was circulating, but hot enough to melt plug wires seems thermostat never opened.

 

[Paulywog0667]

I don't know if maybe tuning carbs just gave way to blow out carbon and coincidence something got hot, but melting plug wires touching where the thermostat goes seems thermostat if water was circulating elsewhere.

The motor hasn't ran the 5 minutes it did in probably at least 5 years.

 

[jimmbo]

Did you replace the impeller prior to the smoke show?

 

[Paulywog0667]

New impeller, it pushed a heavy stream out. I might have messed up the throttle linkage. I had the battery cable bracket removed to put the carbs back on and the choke lever might have budged the linkage. I went back, looked to see. I had a fast idle with a full open lower carb and partial open upper. Which further complicates guessing. It was a fast idle, but probably would have kept going if the plug wire didn't melt until ground out. I don't know what to guess. I could have bumped linkage after. What is the black soot carbon stuff though? What of a bad carb setting would do that and make it hot otherwise? I couldn't get a good idle until backing out needles instead of turning in.

I'm going to compression test, but hoping just a thermostat and hot carbony carb setting. It did fire with the choke, but was still a tad warm and I readjusted back to 1 1/2 and 1 after readjusting the linkage. I never tried leaving a piece of plastic on a car engine block to see if it melts. Would be neat if just needs to cool from the plug wire killing it while carb'd odd.

 

[Paulywog0667]

There was minimal black smoke. A lot of what seems old soot got into the water though. The white smoke just seemed a heavy oil mix. Could have been the black plug wire smoke sucking through the carb and out the exhaust for all I know. I'll test compression. Someone with a 1960s 18hp said carbon and two cycle smoke isn't uncommon. My buddy said ofcourse the thermostat if it's hot, but spitting water. I baught a thermostat.

 

[Paulywog0667]

I compression tested the cylinders. Equal at both cylinders. The top plug is fouled some. For anticipated ring protection I mixed a 32-1 fuel ratio instead of 50-1. I ordered a thermostat and gasket. I'll probably check the points, but hoping blasting it out and swapping to a 50-1 fuel after the thermostat, gets me to testing the shift solenoids and oil pump. I checked the container water it ran in. Soot like a dirty plug at the water level container sides. Maybe the result of points under the flywheel or 32-1 fuel mix.

Further review of the plug wires had them down to the white sheathing under the plastic. I probably had odd timing of it shutting off from heat while catching wire plastic melting. Hopefully the thermostat resolves heat and cleaning or adjusting points at most gets a great idle. The motor started at the standard carb adjustment today. After shock of seeing what may be the end of the outboard and reavaluating, I'm guessing my buddy is right about the thermostat and either the points or fuel mix and blasting it out fouled the plug.

 

[Paulywog0667]

The thermostat hasn't seen water in so long it fell apart. I don't know what the last person did to the spring. It's like they glued it in and wondered why the engine would overheat. Lol

 

[racerone]

???----There are no " points " under the flywheel.-----Your buddy may not be well versed in that outboard motor !

 

[Paulywog0667]

???----There are no " points " under the flywheel.-----Your buddy may not be well versed in that outboard motor !

He is very versed on his 60s 18hp manual start. His thing is body work, but I haven't seen him not fix something. I always ask him the difference in powerpack and charging system. He just did his points and ignition coils. I would guess his logic, but I haven't learned the stator yet. If my thermostat didn't fall apart taking it out, I'd guess the clogged spring blocking flow. I would say he was spot on about the thermostat though. I'm about to research that flow and clean it up before the part gets delivered. The spring came back after breaking off whatever clogged it.

 

[racerone]

This motor has a thermostat and a poppit valve controlled by a spring I believe.

 

[Paulywog0667]

Maybe the lack of a poppit valve has me confused. With the thermostat out, that hole which seems outlet and the hole above it that seems outlet, but with a rubber grommet. The inlet seems to the right.

Unless the spring clogs, it looks like currently there's no reason for a thermostat beyond the bypass opening if where the poppit should go clogs.

 

[Paulywog0667]

Or, no poppit valve, no water volume to cool the engine? Looks like it functions from exhaust pressure. Maybe lack of valve drained faster than filling?

 

[Paulywog0667]

There was an amazing dual stream out the rear of the outboard. Are those from other engine areas? I understand how no valve and stuck open thermostat could mess up idle and rich high throttle. I don't understand the plate burning plug wires unless the clogged spring blocked water travel.

 

[Paulywog0667]

Seem about right? The exhaust keeps the poppit popping and the thermostat runs as needed temperature backup? I included a photo of what I believe is that area's cooling system.

The clogged (filled solid) spring still seems the heat issue. There wouldn't have been more than the inlet side able to spill to the thermostat through a small escape. Anywhere else common heat issues? Since I have one plate off...


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[racerone]

???----Sorry----- but the exhaust has nothing to do with the poppit valve or thermostat !!-----Study the factory manual on how water flows through the motor. ---How it is controlled by the thermostat and poppit valve ----Wild guesses do not work when evaluating an outboard motor.

 

[Paulywog0667]

Looks like a valve shaped for outside pressure to open, not inside water pressure, lol. Will probably pick one up since the upper cylinder is fouling. Still, the heat problem seemed a blocked spring causing no/not enough water to escape. I appreciate the help.

 

[racerone]

The poppit valve opens with water pressure !!!!

 

[Paulywog0667]

What about which side the washer faces? Towards the spring makes sense, but seems a buffer between the grommet too. Is it one of those, they say valve and washer as one piece and the order they go in?