1973 evinrude 25 hp running issues

[jmrix6]

Hello all. I'm new to this site so go easy on me. I have a 1973 evinrude 25 hp model 25302. Last year I was having issues with the motor starting. This year I decided to replace components to make it a more reliable outboard. I replaced the points, condensers, coils, charging coil, impeller, gear case seal, thermostat, fuel pump, carb rebuild and the kill switch. I now start the motor and it runs very rich, smokey and my eyes burn. The motor runs for a few minutes then goes into what is described as a sneeze or a cough then dies out. I have cleaned the carb and taken this this apart roughly 20 times. 2 rebuild kits later I'm still having the same issue. I have soaked it over night in carb cleaned and used an air compressor to blow it out as recommended. I replaced all of the welsh plugs twice and took this motor into a marine mechanic to verify operation. ( $278 dollars after I purchased all of the new parts ) and I still have the same issue. Compression is roughly 100 psi on each cylinder ( I'm located at 10,000 ft elevation ) I've visually inspected the reed cage while the carb was off and see no broken/missing reeds or bent ones for that matter. All fuel lines have been replaced and the marine shop checked for spark and point gap, carb float setting but not timing. I'm stumped as to what is causing this issue. Any help would be appreciated.

 

[F_R]

And just where are you running this thing? In a barrel? That would account for all the smoke in your face. Sneezing at idle is a sign of running too lean. The 10,000 feet is a factor, but not one that I'm familiar with since I'm at 20 feet elevation.

 

[jmrix6]

I'm running it in a barrel. There is so much smoke my eyes burn within 1 minute of running this. I've had this motor 3 years now and it never smoked or ran as rough as this. Mechanic verified that the fuel pump is working. I can see the low speed needle turn all the way in and the carb is super clean. Like I mentioned, every possible replacement part has been replaced. What stumps me is the fact that it smokes terribly and I'm getting that lean sneeze. I'll try anything. Thank you

 

[hardwater fisherman]

If you have a fan use it to simulate running along the water. My motors that run great on the water smoke alot when run in a barrel also. And the low speed needle should not be turned all the way in. Try it with the low speed turned out about 1 and 1/2 turns from gently seated. And adjust it from there. This needs to be done on a boat in the water.

 

[Bosunsmate]

check timing

 

[jmrix6]

The needle was only turned in all the way to verify a clear passage. How do I check the timing? Do I need to purchase a light or a special tool? How does the timing change, and does the timing change without any adjustment from me? Thanks for the input

 

[AlTn]

the base timing is set when you set the point gap, the ignition timing advances when the armature plate rotates as you twist the throttle grip, the relationship of the carb butterfly opening to timing advance is set when you perform the link and sync procedure. The carb roller rest against the timing cam, the timing cam has either a single or double vertical mark, the carb roller should be centered on this mark(s) and the carb butterfly just beginning to open when you have the throttle in a start position. The roller should rise to the highest position on the timing cam when the motor is in forward and the throttle is at wot. The carb butterfly should be exactly horizontal in the carb throat at wot as well.
Are you using fresh fuel mix at 50:1?...did the shop you used adjust on this motor?...did they change the jetting in any way?

 

[F_R]

Of course it sneezes with the needle turned all the way in. That shuts the idle fuel completely off. The smoking probably is caused by oil or crud in the hot exhaust housing. Get it out of that barrel and onto a boat and run it wide open for awhile to clean it out. Then adjust idle mixture properly. You probably will find it is OK.

However--are you sure it is running on both cylinders? If not, the cylinder that is not firing is dumping unburned fuel and oil into the exhaust. All the more reason for it to smoke.

And one last word, those motors had an attempt to burn the oil that collects in the crankcase. They routed it to the upper cylinder for burning. Ha!! All that does is make the upper cylinder rich, and incomplete combustion causes fuel and oil to be dumped into the exhaust. Solution is as before, get it out and run the snot out of it.

Make sure the thermostat isn't stuck open also.

 

[jmrix6]

The shop has verified spark on both cylinders. The tstat was replace but I will check it. The gas is a 50:1 ratio and it is fresh gas. No jetting has been recommended or brought to my attention. I will check the timing later this evening. Thanks again for the input.

 

[60sboater]

That smoky air is going into the engine instead of fresh air. My '72 Johnson 25 also runs pretty smoky in a barrel. Run it on the water,as suggested,after checking link/sync and tell us how it ran.