1976 Evinrude 25 HP idle/excessive smoke issues (Model # 25602E)

[typhoid_iowa]

Greetings!

I have been putting together/rebuilding/replacing a 1976 Evinrude 25hp I bought a couple years ago for my little tin boat. The motor hasn't been run for at least 2 year, more likely 5, since the guy I bought it off of bought it as a parts motor (was originally missing the lower unit, but he found a suitable replacement.) So I've had my fair share of run-ins with little demons throughout this project. But, the motor was the right price, and I love to tinker... so if I can make it useable, its a win in my book!

Anyhow. This morning I set out for the maiden voyage on this old outboard, and had a couple of issues that forced me to pull the boat back up the hill and swap it back to my 9.9 just to salvage the day on the water:

1) I was able to choke and start the motor, and it would idle up as it should (with the choke on.) However, after releasing the choke, it would cough and die. I reset the idle mix screw to both the 1 turn out (as I have read in a few different places,) and also the old tried and true 1 1/2 turns out. Neither of which would proved to make much of a difference.

2) The motor would run if it wasn't at idle, but it smoked excessively. And by excessive, it acted like it was running almost purely on 2 cycle oil. I know the mix was right and it wasn't an issue with the oil separating as the 9.9 didn't smoke at all and started on the first pull.

3) It is pumping water, but it still seems to me that it is running kind of hot. When running, the exhaust housing is very warm to the touch. I know that it doesn't have a thermostat in it (as I was surprised to open the cap to the head and not see an old, corroded thermostat in there.)

Now, just to save a little troubleshooting time, here is a list of what I have done to this machine:
When I started with it, the compression was within 5 lbs on both cylinders (can't remember the exact numbers)
Full carb rebuild
New Fuel pump diaphragm and screen
New fuel lines
New plugs (Went to the OEM spec J4J, had J8 plugs in it when I got it, not sure if I made a mistake there...)
New impeller
All new lower unit seals
Plus a fair number of other parts, since 30+ year old plastic just doesn't cooperate that well...

I've had this motor running in a barrel before I ever put it on the boat, but my barrel size was limited, so I never had a chance to really put this motor in gear and get it up to full throttle before. It has always had the "cough" to it, and it is almost like a typical lean cough, but I can't seem to correct it. And it always smoked quite a bit. I just attributed it to not being ran for so long, it might need a good kick in the pants to clean it out.

So now I'm stuck. Any help would be greatly appreciated, as I would like to know if I'm in a losing battle. I'd hate to sink anymore money and time into this... and I'm sure my wife would hate it more than I would

 

[webrx]

Re: 1976 Evinrude 25 HP idle/excessive smoke issues (Model # 25602E)

I have been going through an 18hp 18202R similar circumstances (search 18202R to find the thread0 it had not run in years, and have thus far cleaned the carb (3 times), replaced one coil, plugs, condensers, points, fuel pump is probably next as it is weak but still working. I have found the fuel mix adjustment has to be right on (mine is at about 1/2 to 3/4 of a turn), as does the carb throttle plate to cam follower adjustment set dead in the middle of the two marks on the stator plate and starts to open the plate when it hits the second mark, in order to stop the coughing. you can also check your plug wires, I had a bad end on one of these. Mine is slowly coming together, but it is like chasing demons with these old engines that have been sitting a while.

Dave

 

[OptsyEagle]

Re: 1976 Evinrude 25 HP idle/excessive smoke issues (Model # 25602E)

A couple of thoughts. I would test the compression and ensure both cylinders are within 10% of each other. I would then pop the flywheel and ensure the points are set properly at a 0.020" gap and are clean. I would also put in a new T-stat. My guess is that the previous owner may have had some fouling problems and perhaps that is why he went to J8 plugs (way too hot). What he should have done is dealt with the fouling problem, most likely due to a lack of a T-stat or perhaps too low of point gap.

I suspect that you are having trouble getting it to the proper temperature, which is required before you set your slow speed needle on the carb. If the points are set fine and you are getting a good spark (using an external spark tester it should jump a 3/8" gap on both cylinders) and compression, and you have fuel in the bowl, the motor should start with the carb needle set 1.5 turns out from seated. It will run rough, but let it come to temperature keeping a fast ldle on it. Then just reduce the throttle until it just runs and slowly turn in the idle adjust, 1/8 of a turn at a time. Give it 10 seconds to respond. Keep reducing the throttle and keep turning in the carb adjust until it pops and wants to die. Turn it back (counter-clockwise) about 1/4 turn and you are good to go.

If you cannot get it to run initially, and your spark and compression is good, it would look like your carb is still dirty. You could try and spray some pre-mix fuel directly into the carb throat and see if it runs for a little to determine that.

If you do get it running, you will want to do a decarb on this motor. If he was running without a t-stat for a long time, I would suspect the motor was carboning up and is probably why it smokes so much.

Those are my thoughts.

 

[lindy46]

Re: 1976 Evinrude 25 HP idle/excessive smoke issues (Model # 25602E)

When you rebuilt the carb, did you remove the welch plug and clean the passages in the idle circuit? Something isn't right there, as adjusting the needles should make a notable difference in the way the motor runs. I agree with the decarb - at least run some Seafoam in your gas - 2 ounces per gallon. That will help clean things out.

 

[typhoid_iowa]

Re: 1976 Evinrude 25 HP idle/excessive smoke issues (Model # 25602E)

Thanks you guys for the quick response! I now have a couple of different avenues to go down in hopes of bringing this thing to life. I had wondered about a decarb, and after a little more thought, that would make some sense. I also think I'm going to put in a tell-tale, just to make it easier to make sure it is cooling.