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?1970? Evinrude 25hp smoking

D

DRuben

New member
Bought the boat a few months ago as my first boat. What I have noticed is that it tends to smoke a bit. I’ve tried different fuel/oil mixtures but it still smokes. It runs fine and I ran it for a few seconds outside of the water and it still smoked but not as much. I’m fairly good hands on with larger engines so I’m sure I will have no problem working on a small engine. Here is an included video: https://youtu.be/dmlws-X4q2w
 
Beautiful motor. Seems it could be a bit rich on low speed mixture. Try turning in low speed needle until lightly seated, then back out 1 1/2 turns and follow Joe Reeves tuning proceedure. What kind of oil are you using? What is your mixing ratio? You can also go to Amsoil fully synthetic at 64:1. I run mine at 100:1, but I constantly am belittled by some certain other techs here. Have done my mixing ratios with Amsoil 100:1 2 stroke pre mix synthetic with hundreds of outboards since 1980. I have 2 remote camps on large NW Ontario Lakes, where a motor failure can cost your life. Never yet have I done any harm to my outboards in 40 years now. Some have close to 3500 hours on them! However, I have no personal experience running ethanol fuel........I simply don't allow it. I do however have hundreds of repairs related to ethanol damage in my customer's equipment. I could go on, but your main problem is either too much oil or a rich low speed mixture setting....or a combination of both. 50:1 is required with any oil other than Amsoil 100:1 2 stroke pre mix or Amsoil Saber 2 stroke pre mix. Racer is 100 percent trustworthy. We were typing in at the same time here. Joe will likely chime in, but otherwise check his other recent post #5 on 15 hp Evinrude problem "Starts and Stops".
 
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That looks normal. I believe you have a thermostat in that motor check it to make sure its not stuck. 2 reasons you have smoke like that, #1 you are in a barrel, #2 the motor is not up to temp. Get a thermostat in it and get it on the lake. But 2 strks always smoke a bit because they burn the oil in the gas mix. Do not play with the mix 50-1 is the factory mix for that motor. Some synthetics allow you to mix a leaner ratio.
 
It is supposed to smoke!!! You notice it more because it is in that tub. It is running well, so no need to monkey with the adjustments either. Maybe just a slight tweak once you get it on the lake where it was designed to run. But it will always smoke a little bit, somewhat depending on the oil you use. If it doesn't smoke at all, you got trouble
 
I have a 25 exactly like yours, but only a couple years newer. Mine seems to idle more smoothly as well as slower. When you pulled your motor into gear the idle seemed high also as represented by the hard jerk. Compression can and will have an effect on power overall, thereby affecting how well it performs and its ability to idle smoothly. I wonder what is your compression, and have you been able to adjust your low speed any better by using the proper method. New plugs, prefer Champion, and set at .025. Thank you for your help Mr. Scott and Gator. You are correct in saying that they will almost always smoke more in the barrel run. Mr. Ruben may wonder why. Well it's because the intake picks up monoxide, and other contaminants from the "stale" air. This creates an automatic rich burn because the motor can't breath very well. This in turn aggravates your ability to effectively tune your motor in a tub or barrel. I have a decent size fan on a stand that I can set up in order to blow away the dead or stale air, allowing me an effective tune. The cowling will negatively affect things too, so once you put the cowling back in place, it will often richen things up a bit......for surely if tuning it in a tub, the cowling will really mess things up. On some outboards I drill holes in the lower cowling in order to help introduce fresh air, but when trolling, depending on mixture, wind, direction of travel, and boat design......it can be difficult to get a good fresh air supply for intake. I am a fishing guide and most of my boat time is spent trolling. I really have enjoyed the freedom of fresh air around me as for 40 years I have used Amsoil at leaner ratios. It really is a fantastic product, and probably helped extend my healthy life. 4 strokes are too heavy to handle in portaging and setting up/tearing down boats at our Ontario Canada camps....and I often have little or no help. It has always been 2 strokes, and always will be until I quit.
 
Follow Tim's advice and make sure you're low speed mixture screw is set properly and you're at the correct idle speed. Also, verify you have the correct spark plugs and good spark on each cylinder. It looks like you should have Champion RJ8C plugs in that engine. As FlyingScott mentioned, make sure the thermostat is present and operating. A cold engine will smoke more for sure.

As everyone else said, it's a carbureted 2-stroke engine.....IT WILL SMOKE. The smoke you have doesn't seem excessive, but it still won't hurt if you check carb adjustment, plugs, and spark to make sure you're getting optimal combustion.

What oil have you been using in the engine? You need to be running a low ash TCW3 oil at a 50:1 ratio. I have a '79 Evinrude 9.9 and I use Evinrude Premium 2-Stroke oil in this engine. This is a mineral based oil but it burns clean with very low smoke: https://www.amazon.com/Evinrude-Johnson-2-Stroke-Outboard-Mineral/dp/B005EZ15RS You can usually get this for less than $20/gallon at Walmart. I also suggest you use a 2-stroke mixing bottle. You can get these for under $5 at Walmart and is a great way to make sure you're always adding the right amount of oil.

KJ
 
Another note....and thanks, Kevin.....good solid advice, If the motor has been habitually over oiled and with lower quality oils, perhaps. It may be "carboned up", thereby causing ineffective evacuation of the exhaust gasses. When the new mixture charge comes in to the cylinder, it will be contaminated with poorly combustible oil residual air. What happens next is incomplete combustion which is reducing power, fouling plugs, building more carbon, and producing smoke and unhealthy air around the stern........where did the owner of this 25 hp run off to now? We are having a great discussion with ourselves. Maybe he turned in the mixture screw and never looked back?
Here is a photo of my 25, idling after 10 minutes....
Mostly water vapor, temp was only 50 degrees F. Notice that it is in gear. If it was on a boat there would be even less smoke. 1547759451423399.jpg
 
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And yes, there is a prop on my motor. There is very little turbulence in the water So you know that it is a slow, smooth idle. The motor in the video would flunk big time for me, if that's as slow, or smooth as it will idle. A 25 needs to be much better than that, or it would never be returned to the customer.
 
Sorry been working too much. Before the video I screwed with the idle and forgot to put it back but it does idle slow and smooth. I’m curious about a thermostat and it’s location though.
 
Also I’m not too sure about the mixture being that it’s from the previous owner but I’ll empty and start fresh. It has champion j4c plugs, both brand new
 
50-1 is your mix. Look on this website for your model #. The thermostat is listed under powerhead group. You will need 3 pieces, Aa new cover gasket,thermostat and thermostat gasket.
 
http://www.marineengine.com/parts/j...&manufacturer=Johnson&section=Powerhead+Group

Cover Gasket
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0308328

Thermostat seal
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0310058

Thermostat
http://www.marineengine.com/newparts/part_details.php?pnum=OMC5005440

Sometimes owners thought overheating was a bad thermostat so they pulled them out. More often it's 2 other causes: 1) bad water pump or 2) plugged water passages. Usually the water pump is the culprit.

If you have no knowledge of the pump age/condition it's a safe bet to replace the pump so you know you're getting good water flow. You have 2 options to either replace the entire pump or just the impeller. I usually replace the entire thing, but if the housing is okay you can get by with just an impeller.

Water pump kit:
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0382468

Impeller Only:
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0775518
 
J4 plugs are too cold. If your running the previous owners mix, that could be the main problem. Use that stuff up in your 1974 Chev truck and mix a new batch of Amsoil 100:1 2 stroke pre mix oil with non oxy fuel. Now so I don't get blasted by my fellow techs, I will recommend a little richer ratio than I use myself in the 25 hp pictured. Mix at simply 2 oz per gallon, or 64:1. You will never use another 2 stroke oil again. Trust me....40 years on Amsoil, brah! I run J6C plugs in mine, change them every 2 years, whether it needs them or not. If you elect to go 40 or 50 to 1 on petro based oil, you can go J8C......you will NEED a hotter plug. The lack of thermostat as well as heavy oil ratios will cause carbon build up. Did you read my earlier info on that subject? See # 8 post.
 
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I’m gonna swap the plugs when I get off and probably put the old gas into my waste container since I don’t have anything else that’s gas powered and don’t want to put a trash mix into my weed eater
 
J4C is the factory RECOMENDED plug for.your motor. Use a good quality tcw-3 mixed at 50-1 and go boating. Also put the thermostat back in. That motor has run for 40 + yrs as it is no need to reinvent the wheel here.You ABSOLUTELY do not need to change your plugs for anything else. Thousands of those motors with the J4c plugs in them.If you decide to use a synthetic oil there are other options out there besides Amsoil. Amsoil is not even TCW-3 rated for 2 strks.
 
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Mr. Scott, how many quarts of Amsoil have you run through 25 hp motors at your lake home or resort? Your trying to tell us how to sky dive and you've never strapped on a parachute. I have experience, don't always follow "recommendations". I follow WHAT WORKS! THERE IS A H*!! of a lot more truth in experience, than in the words of one that never took that jump.
 
I believe that running without a stat stops the motor getting to temperature.This causes some of the two stroke oil to get blown through without burning off.
Like has been mentioned earlier,the motor needs oxygen,if it is pulling in smoke you don't get the correct burn.
 
How come this turned into such a battle ground? The man said his motor runs well but he was simply concerned about the smoke.
 
Smoking is directly related to many variables, but some here are ignorant to anything that isn't "factory recommended"......50 years ago. "Times They Are A'changin". The factory recommends regular LEADED fuel.....who does that? Back in 1970 we had some good hot fuel, real fuel. The closest we can get today is 91 or 92 octane non oxygenated.
 
Sorry-----It should idle slower and smoother than what it is doing in the video.------Need a fan blowing exhaust away too.
 
That runs rough. Needs more work. Revisit the information above. Have you checked compression? Always the first thing to do before deciding what to do with a motor.
 
DRuben said:
Got the new thermostat in
Click to expand...

What is the model number of that engine?..... If it's been mentioned, it's hiding. :)

Champion spark plugs J4C or J6C are generally recommended. Due to age, the J6C may (but not always) provide a somewhat improved performance... something to keep in mind.

If that carburetor incorporates a throttle roller..... If the roller is even slightly worn, grooved, whatever, replace it. The adjustment of the roller should be set so that the throttle butterfly just starts to open when the scribe mark of the cam is dead center with the roller... not before or after.

If the carburetor has an adjustable slow speed needle valve... adjust as follows:
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
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