black soot

[Barracuda101]

1990 evinrude 140 hp here's the question: i have alot of black soot coming from the port on the lower coweling and this engine runs good at high rpm but at idle and trolling speed its a little rough. the other engine doesnot have this problem. if some of you guys recall these are the engines you helped me with in the past 6 months. the first time i have had it out this year and everything was great but that little problem. any help would be great. Thanks

 

[tashasdaddy]

Re: black soot

do a decarb. clean the engine out. see Faq forum for decarb.

 

[Barracuda101]

Re: black soot

I looked for the decarb instructions in the FAQ and could not find anything on it. what is the process please

 

[Tacklewasher]

Re: black soot

It's on the second page. I know I missed it at first.

http://forums.iboats.com/showthread.php?t=158076

 

[Barracuda101]

Re: black soot

Can i do it with the garden hose and ears or does it have to be in the water?

 

[ezeke]

Re: black soot

You can do the de-carbon treatment on muffs, but wait until the neighbors have their windows closed - it makes a lot of smoke.

I have the same engine as you, but from 1988. The soot at the exhaust relief is common when trolling, but synthetic oil and thermostats that work correctly will help.

A liitle WD-40 on a rag will clean off most of that carbon.

After you finish the de-carbon treatment, your recirculation check valves will probably be clogged and need to be serviced, but they may already be clogged and part of your current problem.

 

[Barracuda101]

Re: black soot

What are the recirculation check valves and where are they located? I'm not familiar with this part. How do you service them?

 

[ezeke]

Re: black soot

There is a recirculation fitting on the side of each of the cylinders connected to a small black hose.

The hoses lead to 4 recirculation check valves on the intake side of the crankcase. Pooled, unused fuel and oil from the cylinders is circulated back to the forward area of the crankcase to remix with incoming fuel from the carburetors.

Properly functioning check valves allow flow in only one direction. If they are clogged or stuck open, you can have a variety of problems.

Use a syringe and hardware store isopropyl alcohol to test the check valves. You can use the black hoses. The alcohol should flow in when you depress the syringe, but not out when you pull out on the syringe.

The fittings at the cylinders are not check valves but also need to be open.

I have had limited success with clogged check valves. Soaking them in alcohol will sometimes make them serviceable. If they are not functioning properly, it is best to replace them.