83 115 smokes at idle and start

[txbandit44]

I have good compression 118psi in all 4 cyl, just rebuilt carbs fuel mix is good dead on at 50:1. I do have a intermitant miss at idle. I get a bit of smoke at idle and while trolling at idle in gear. I would say it looks like a as if someone was able to blow cigarette smoke continously. But at start up after running for a while and the sitting for about 10 15 min i get alot of smoke..

What could cuase this or is it normal?

 

[noelm]

Re: 83 115 smokes at idle and start

I guess from what you are saying, you are mixing fuel yourself, and that being the case, the smoke is from the oil mixed with the fuel (of course) and there is no way to adjust it so you do not get smoke at idle, you need 50:1 for high speed running, but at idle you only need 70 or 90:1 hence smoke, the very reason, VRO/OMS was invented.

 

[jonesg]

Re: 83 115 smokes at idle and start

Examine your sparkplugs just in case its steam, look for a steam cleaned plug.

 

[tashasdaddy]

Re: 83 115 smokes at idle and start

suggest doing a decarb, and get rid of the excess carbon build up in the engine.

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.

 

[emdsapmgr]

Re: 83 115 smokes at idle and start

The engine will smoke a lot if it is running cool. The combustion process is not as good. Thermostats which are stuck open will cause cool powerhead temps. Also, if the pressure relief valves are stuck partially open, that can also cause cool temps. I'd borrow a laser temp gun and check the head temps at idle when the engine is warmed up. Should be in the 145-155 degree range. An intermittent miss at idle can be a lean sneeze, which can be caused by a lean idle situation on one carb or slightly advanced idle timing or a carb butterfly which is slightly open. The decarb metioned by Tas is a good idea.

 

[kenmyfam]

Re: 83 115 smokes at idle and start

I have always got a nice cloud of smoke at initial start up from cold on my 140 hp motor. Clears straight up and off we go. As said you do not need 50 to 1 ratio at idle and trolling speeds so there will be excess oil in the system and it will smoke a little more.
Agree with the decarb.

 

[emdsapmgr]

Re: 83 115 smokes at idle and start

If you tilt the engine up frequently after running, this can cause some of the problem. Not unusual for these carbs to leak a little excess fuel when the engine is tilted up high. The excess fuel pools in the bottom of the airbox. When you tilt the engine down for a restart, the excess fuel is ingested into the bottom cylinder through the airbox drain hose and may cause excessive smoking for a minute until it is burned off. (a normal situation.)

 

[txbandit44]

Re: 83 115 smokes at idle and start

Thanks for the replies.
I will do the decarb and replace the t-stats. This is a really clean low hour motor. My boss owned the boat since new and used it once or twice a month. So i think the mix is really the issue but being that it is so old I am going to do it all.

Now I just need to get the trim fixed and Ill be back out in no time.

 

[cougar1985]

Re: 83 115 smokes at idle and start

just did a decarb on my 90 evinrude but i did it slightly different than whats been suggested here but with very good results.took plugs out ,sprayed in deep creep penetrating oil!put plugs back in ,let sit for a hour or 2 then started up the beast.may i say that there are no more mosquitoes around now as she smoked pretty good.i always add seafoam to the gas about every 3rd or 4th tank as preventive medicine also.