98 Evinrude 50hp off idle miss

[EE]

Hello, I have a 98 Evinrude 50hp two cylinder. I have many years of automotive experience but have not worked on many two stroke outboards. Ever since I bought the boat it has always idled a little rough. Now it has an off idle shake. When it does shake it smokes more. Always starts up and has plenty of power and top end once you get pass the shake. The compression is 150 and 142psi, the carbs have been rebuilt and are very clean. I did the whole sync proscedure according to the manual. Tried adjusting the carb mixture but does not solve the problem. The idle timing in forward is 0 degree which is what the manual calls for. The thermostat is working correctly. The plugs are new and are properly gapped at .030. I use it in the summer and winter to fish so new fuel is being added on a regular basis. When I pulled the carbs off I looked at the reed valves and they appeared to be all closed and not broken. I dont know much about reed valves. Do they get weak after awhile? Not sure where to go from here. Great site and any help is greatly appreciated.

 

[1946Zephyr]

Re: 98 Evinrude 50hp off idle miss

this got posted twice. How did that happen?

 

[5150abf]

Re: 98 Evinrude 50hp off idle miss

Welcome to iboats.

When you rebuilt the carbs did you actually phsically clean all the jets?

There are 3 jets and unless you ran a wire through them your carbs are not clean and the problem will continue until you do this, also good to blow air through the passages between jets.

You can get a dental syringe from CVS and squirt a bit of gas into the cylinders when it is running, if it suddenly runs better you found your clogged carb.

I think you are running on one cylinder, it is really hard to pick up a miss on a 2 stroke.

 

[EE]

Re: 98 Evinrude 50hp off idle miss

Hey thanks for the quick response! When I rebuilt the carbs I shot pressurized carb clean thru the jets and could see it squirt thru. I then ran shop air thru all of the jets. I did not physically run any wire thru them. Since we are on the topic of carbs. When I had one of them apart it has the jet inside of another that runs down the throat of the venturi. The inside one was not centered inside the other. I dont know if that makes a difference and I did not straighten it. By the way you can't feel the problem if you run the engine with the muffs, it has to have a load on it. Sounds like I will take your advice and try adding fuel down the carbs when it does the problem.

 

[5150abf]

Re: 98 Evinrude 50hp off idle miss

Ya, squirting the cleaner through the jets really doesn't do anyhting, you have to physically clen them.
I just get an old copper wire and pull back wires till it just fits.

Mine "lookled" really clean btu the problem didn't go away until I ran the wire through them.

 

[tashasdaddy]

Re: 98 Evinrude 50hp off idle miss

suggest reading carb cleaning. http://forums.iboats.com/showthread.php?t=299680

 

[EE]

Re: 98 Evinrude 50hp off idle miss

Ok looks like it is a fuel issue. I pulled the carbs today and cleaned all of the jets with a wire and cleaner. I didnt see anything coming out. These carbs look great. Decided to check float level and it was off by a fair amount. Not sure if the rebuild kit I got originally had the wrong specs but I now have the book and used the specs from it. The float level was to lean. Put the carbs back together and ran it in a garbage can and it idles great!!! Well as good as a two cylinder can idle. I have a lot better control with the idle mixture screws. Cant run it very fast but I bring it just off idle and no miss. I will take it out on the water and adjust the mixture and see what happens. You would think the float level would affect top end more than low speed? Anyway thanks for getting me back into the carbs and I will let you know how the test run goes

 

[EE]

Re: 98 Evinrude 50hp off idle miss

Finally got to test the boat out while fishing. It runs smooth off idle all the way to full throttle. It idles a little rough, but I think the two cylinders do. I played with the idle mixture and think I got it pretty close. Thanks for the help!!!