Onan Smoke

[doc g]

Chris ,I think what was mentioned was that if a stat was stuck open you could be too cold at no load and therefore incompletely combusting fuel.....Pat

[Brian Degulis]

Okay I guess I may be describing the smoke wrong, its definitely blue, light blue but not white, not black and no fuel in water. I changed the impeller this winter and I get a lot of water flow from the exhaust, so I don't think its a heating problem. its a very noticeable smoke when first started and cold, it seems like a lot to me but the admiral says its not that bad, when we are under way (@10kts) you can see a slight blue haze down the port side when I first start it. under load 50% - 100% no smoke at all, as soon as I shut everything off to let it cool it immediately starts smoking just like a cold start.

Hi Chris

Your second description above makes me believe even stronger you have thermostat stuck open. So as soon as you take the load off it starts running to cold and starts smoking again.

If you want to check for this just get yourself an infrared heat gun shoot it hot under load then shoot it in the same spot with no load and smoking. If there is a big diffrence then more than likely all you need is a thermostat.

I only threw out the diffrent colors of smoke to say that yeah blue is oil and white is cold smoke but sometimes the color is not such a clear line. If your not using oil your not burning it. Lots of engines smoke blue when they're cold and it's not oil it's incomplete combustion from being cold.

Brian

[chris piazza]

Actually I think the PO left a thermostat on the boat. IF he did it would be a quick repair. It does make some sense that it is the thermostat because I am not using any oil and I have a tremendous water flow that doesn't appear to increase or decrease like it would if the thermostat was working. I don't have an IR gun (I know, I need one) but changing it out is not a big deal and would eliminate one possibility of the smoking before I go pulling rocker arms and valves.

Chris

[yachtsmanbill]

Hey Chris-- on another note, you need to check the oil return standpipes under the rocker covers. Just a PM thing. Look in the manual ! I also thought of you
(and me) when I saw this the other day on ebat. ws
Item number: 260128237532 12 hours left !!

[yachtsmanbill]

This is what it looks like... ws

[MikeP]

"I have a tremendous water flow that doesn't appear to increase or decrease like it would if the thermostat was working"

If you are talking about the water you see from the exhaust, the RW flow does not change based on the thermostat. The RW flow (what you see coming out the exhaust) is constant at any given RPM. The thermostat controls the flow of coolant in the circulating Fresh Water system of the engine itself which is not visible in any way.

[chris piazza]

Mike your right about the water flow, wasn't thinking I am definitely going to change out the thermostat this weekend, keep it simple right!

Bill, that looks just like my stop solenoid, I went over mine last weekend and adjusted the ram down about two turns and its working fine now.

Chris

[chris piazza]

Okay, I pulled out the old thermostat and it was in the closed position when I pulled it out. I decided to test it in a pan of water and it cycled several times closed to open with no problems. My question is is this a fair test, should I assume this is not my problem with the smoke and reinstall the thermostat or track down a new one and put in it just to be sure?

[Brian Degulis]

Assuming it opened at the right temp yes that should be a fair test. I think I would still replace it while your there. And I think I would also check the temps smoking and not if for no other reason than to eliminate it as a posable cause.

Brian