2-stroke lots of smoke

Okay gearheads I need some help.

I've got a 1981 Spirit 8 (same as a Suzuki dt8) on my boat. Thing is, it smokes like chitty chitty bang bang while I'm trolling. I had a carb kit and tune up done 3 years ago after not running it for a few years.

1- Is this normal with a 2-stroke?
2- Could it be that I need to run a 100:1 oil ratio instead of 50:1?

Normal 2 stroke smoke screen? yes. Some more than other thats for sure! Given the age of the ol' girl shes gunna be a smoker. The newer ones tend to burn much cleaner. I wouldnt change the ratio, youll burn it up. How bad is bad?

I use to have an old 1950's Merc Mark 55 40HP. One of the best 2strokers I have ever used. Oil ratio was originally was 25:1. With modern technology of oils that has increased 40:1... The smoke trail changed quite a bit. I would suggest checking with the manufacturer or local marine shop for info regarding the type of oil to use and what ratio. The old days of chitty chitty bang bang are coming to an end.

could be too rich on the idle screw.
with access to carb mixture screws at troll rpm adjust idle slow speed screw in until engine starts to slow down. turn back out 1/4 turn. do same for high speed mixture screw at wide open throttle.

use full synthetic such as Amsoil TW-W3 outboard oil, far less of it burns at slow troll rpm, not enough heat. Can get by even in the older motors at 75:1 mix with full synthetic oil if used mostly for trolling and less than 25% wide open runs.

Pennzoil makes a 100% synthetic OB oil but hard to find, they have their partial synthetic at WM that smokes somewhat less than the cheap crude oil stuff.

engine may also need to be decarboned, stuck rings and carbon buildup on heads, piston tops and exhaust ports. makes for lots of misfires and smoking.
some carbon gas cleaner additive such as Techron or my favorite, 1 qt of acetone in 6 gallons of gas and a spray bottle of acetone to spray in carb throats at full throttle on the water. watch the black crude blow out.

Thanks guys. I had swapped brands of plugs to try champions this Spring so I just pulled those and put the ngk's back in.

I think I'm going to dump the last gallon of gas and try a new oil to see if that helps too. I can't remember it smoking as much at idle with the pennzoil, so maybe it's the West Marine tcw that's adding to the issue.

Have any of you tried the Mercury "Rejuvenate"?

Which stores carry the Amsoil?

Motors used a lot for trolling tend to produce a lot of their own oil. Consider running some seafoam through the engine to help clean a lot of the sludge build up.

MackPrince said:

Thanks guys. I had swapped brands of plugs to try champions this Spring so I just pulled those and put the ngk's back in.

I think I'm going to dump the last gallon of gas and try a new oil to see if that helps too. I can't remember it smoking as much at idle with the pennzoil, so maybe it's the West Marine tcw that's adding to the issue.

Have any of you tried the Mercury "Rejuvenate"?

Which stores carry the Amsoil?

Click to expand...

I have had a very low success rate using Champion plugs. AC, Nippodensos, NGK and even Autolite gave me better performance. Seems like the only time Champions worked is when I bought a new gas power tool of some sort. Replacing them with the same part number they would immediately foul out.

MackPrince said:

Which stores carry the Amsoil?

Click to expand...

I've started using Amsoil in my 9.9 Merc and it's been great so far. 100:1 ratio.

They have two types of 2 stroke to use, for power tools (which I use) and for outboards if you can find it.

Some autoparts stores, such as some NAPA dealers carry Amsoil.

Check thier website. They can direct you to a local dealer near you.

Mix ratio's are what the manufacture has determined will provide the required lubrication for that engine in a wide variety of operating areas but not necessarily for optimum use of the mixture, it also is designed to provide the required lubrication when the motor is operating under max load. The amount of oil needed when at idle is no where near what is required when running at full throttle or on a "hole" shot, hence the addition of oil injection systems but that's a different discussion. Most motors are set up to operate at sea level and if the carb hasn't been "jetted" for the altitude it's operating at then it could be also getting more fuel then is needed. The unused and residual fuel oil mixture will result in the heavy smoking at at low speeds.

Thanks guys.

I pooled that info and decided to do a little in-home tune up.

Checked the gas - Had 3 gallons in the tank so decided not to dump and use synthetic yet. Instead added 1 quart of gasoline to bring the ratio closer to 64:1.

Pulled the new spark plugs - After just 5 hours of trolling the Champions were beginning to glaze. Tossed 'em and replaced with NGK.

Internal - With the plugs pulled I used some carb cleaner in the air intake, carb and cylinders. Internal parts had minimal carbon for being 31 years old. Carb was clean. Adjusted the air jet at idle out about 1/4 turn to increase air mix.

Lower unit - drained and replaced lube. No water in oil.

Exhaust/cooling system - I noticed grease/oil build-up near the three above-water exhaust holes. Opened the gear box and checked for wear or leaking grease from seals. Cleaned all the ports and any accessible areas.

Greased the gaskets/zerks.

How'd it run. Saturday it seemed to run well. No signs or sounds of running hot, smoke was less than the week before (but still some telltale 2-stroke exhaust), and had no issues with fouled plugs or stalling out. I'm planning to switch to a synthetic tc-w3 once I burn through this tank of gas.

It's hard to tell if a carburetor is clean. Some of the jets can have a hole that's the size of a human hair. All it takes is enough time without running to evaporate the gas and leave a plug of gunk in a jet. Did you completely disassemble it and soak it in carb cleaner?

The only other thing I can think of is to run Stabil into it at 100% concentration like it says on the bottle. Then after the recommended soaking time, run it on the lake. You will likely get a lot of smoke initially as it burns off the carbon. It will also likely un-stick any sticky rings. Good Luck!