71, 40hp johnson, smoking pretty bad?

[1970kayhydro]

I have a 1971 40hp johnson, i just rebuilt the carb and still smoking. The points and condensers are new also. I am pretty sure the gas is mixed 50/1 properly and no matter how the carb is adjusted it blows alot of smoke and it seemes to be worse when i tank test it and not so bad when i take it to the lake. Although i have not taken it to the lake sence the carb rebuild, i was told that was why it was smoking. Any ideas?

 

[david_r]

Re: 71, 40hp johnson, smoking pretty bad?

i have a johnny '79 115 (just bought it about 2 months or so ago).

anyway i was reading the threads and doing preventive maintenance and ran across some decarb threads so i went to the faqs and got more info....long story short improved idle and a lot less smoke when idleing and at start.

smokes like a freight train when doin the decarb though.

 

[msimon]

Re: 71, 40hp johnson, smoking pretty bad?

It's not uncommon for it to appear to smoke more in the tank or on the boat at idle. While running in the water at higher speeds more of the exhaust makes it down the housing to the lower exhaust port.

Make sure both needles are adjusted correctly and you are using the proper spark plugs. (J4C's at .030)
To adjust the low speed needle, start with it approx. 1 - 2 turns out. Adjust it in (to the right) until the engine is "spitting" this means it needs a little more fuel, adjust it back out just till it stops spitting.
It's best to adjust the high speed needle on the water at WOT unless you have the correct test tank and test prop. Obviously, you will need someone driving the boat to do this. Open the needle out 1 - 2 turns, run at WOT and adjust accordingly. You'll now when you get it right.

 

[tashasdaddy]

Re: 71, 40hp johnson, smoking pretty bad?

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Thanks for the replies. Im going to decarb the motor, i live about 15 miles from the launch and then its no wake for about 1/4 mile so its alot easer to do it here. What would be the best way, i have a bottle of seafoam but not the spray one. I just did the carb rebuild and cleaned it real good with seafoam and replaced all the parts (float, seals, carb kit). Smoke isn't too big of a deal here.

 

[tashasdaddy]

Re: 71, 40hp johnson, smoking pretty bad?

the seafoam spray can is the same stuff as you put in the fuel, just put some into a spray bottle, and spray into the carbs. remember afterward atleast clean or replace the plugs. it is also going to make a mess on the ground where the exhaust, and water comes out. so don't do on a concrete driveway.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

It started to work at first then still alot of smoke. I pulled the plugs, top was real clean and the bottom was not that bad, but dirty. I poured seafoam in the cylinders and let it sit. I helped but now it doesn't want to idle and its cutting out every few seconds. It sounds better and most of the smoke is gone but only at a 1/4 throttle. I let it run for about 5-10 mins.

 

[david_r]

Re: 71, 40hp johnson, smoking pretty bad?

are you using fresh gas?

i had some weed eater gas in my shed that got overlooked and never used and all the gas evaporated and left the oil behind.....is there any chance it has sit without seein the drink for a while allowing the gas to become stale and rich w/oil?

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Gas was fresh about 3 weeks ago. Im going to try to run it longer/more and see if it doesn't clear up. Im more wondering why its cutting out now?

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Its still smoking bad, how do i need to let it run? I don't want to **** off the few people who do live close by.

 

[kenmyfam]

Re: 71, 40hp johnson, smoking pretty bad?

You need to take it to water and gun it.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Can i just bring the rpms up some and let it smoke out, or should i try it again when im ready to take it to the river? Its just a big pain to take it up there and putt up to where i can plane it out for it to not run good at all, its happened a few times. Like i said its a ways to go of no wake, about 1/4-1/2 mile.

 

[david_r]

Re: 71, 40hp johnson, smoking pretty bad?

i know that if you do it like the faq says it takes a while.

i did the whole process with the soaking then mixing the gas and seafoam and had to run it three times doin the drive 15min and wait 15min. my 16yr son and i was at the lake for a couple of hrs and used the whole gal of gas putterin around and killin skeeters.

i was thinkin of decarbing my small obs in a tank but not sure i want to try that after seeing the smoke from the first one.

your cutting out could be the seafoam still burning off carbon deposits.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Could it hurt anything if i spray seafoam in the carb again, maybe still some goo in there? It's getting better.

 

[tashasdaddy]

Re: 71, 40hp johnson, smoking pretty bad?

seafoam will not clean the carb, but will clean the motor, it will not hurt anything to keep doing if. also after the carb rebuild get the carbs adjusted properly, this has to be done on the water.

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top 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. Again, 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 adjustments, 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.

 

[david_r]

Re: 71, 40hp johnson, smoking pretty bad?

as long as you have a good oil/fuel mix i dont think there is such a thing as too clean, but more seafoam will probably produce more smoke unless shes clean from carbon but thats the whole idea, to clean all the carbon.

during my decarb i had to use the fast idle lever when i came up to the dock to let her idle for the few remaining mins of my cycles, otherwise she wouldnt idle till she was rid of the junk.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

I just did the full carb rebuild so its clean. The smoke is going away but its still running odd.

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

Ok i took it out today and it ran Great planed right out in seconds went fast, but it was shaking or maybe missing on the out of the no wake area. When I opened it up it ran real strong and good next to no smoke. I put premium gas, fresh oil, carb kit, and new plugs. Is it normal for it to be shakey at low speeds?

 

[david_r]

Re: 71, 40hp johnson, smoking pretty bad?

its a 2 stroke (even a car motor shakes a little)so its gonna shake some does it sputter sneeze or cough? however it shouldnt act like its gonna jump off the boat(ive seen one try)

did it act like this before the decarb?

hows your compression after the decarb? mine gained a little(very little)!

are you dropping a cyl at idle? best way to check is put a timing light on each wire or you can take one for the team and pull the wires off one at a time.....you may want to see whos in the 1/2 mile area before you do the latter

 

[1970kayhydro]

Re: 71, 40hp johnson, smoking pretty bad?

It barley ran before the carb kit, decarb and plugs. Its not that bad, you can't really feel it in the boat just when I look back i can see it back there shaking it's only moving about a inch while its doing this. As soon as I open it up it gets right up on the water and planes out real quick and runs great. I am guessing its probably going 35+ mph how, fast should it go Its pretty light maybe 500-600 lbs with the motor.