9.9hp 2t outboard oil help

[1978elcamino]

Hi all, I have a 1991 Evinrude 9.9 two stroke, new to me but is in almost brand new condition. I have been through the carb (pulled apart the carb just to look) and the engine runs PERFECT. My problem is @ 50:1 the engine smokes a lot at idle, which is normal I understand. Once underway and for the few minutes after WOT brought back down to idle it does not smoke. My issue is that once it cools down and idles it begins to smoke and thats a problem because I troll a lot. This outboard is on a jon boat so the motor is practically right next to me when Im driving. So, my question is, I want to run an oil mixture of say 70:1 or 80:1 to mitigate the smoke while trolling, what oil will provide the best protection at a higher fuel to oil raito? Before anyone gets into the mixture screw conversation I will say I have spent plenty of time adjusting it and it is set PERFECTLY and runs excellent. Current oil is Penns tcw-3 semi synthetic @ 50:1. Again, minimal smoke but once the motor cools for a few minutes it begins to smoke at my 2mph trolling speed.

 

[bullwinkle]

I can't remember any 2 stroke outboard I've ever had that DIDN’T smoke at low speed-thought that was the purpose of a trolling motor?

 

[1978elcamino]

I can't remember any 2 stroke outboard I've ever had that DIDN’T smoke at low speed-thought that was the purpose of a trolling motor?

I gotcha, I really do. I guess I should have said that I have a trolling motor but with a full battery I only get about 85 minutes of running out of it at my desired speed. And the goal is not to eliminate the smoke completely but reduce it by quite a bit. Oddly enough, my 125 mercury 2t has ZERO smoke at idle / trolling speed with the same oil. The difference is the Mercury 125 has oil injection that goes to a much higher fuel to oil ratio at low / slow speeds.

 

[MichiganMadMan]

Hi all, I have a 1991 Evinrude 9.9 two stroke, new to me but is in almost brand new condition. I have been through the carb (pulled apart the carb just to look) and the engine runs PERFECT. My problem is @ 50:1 the engine smokes a lot at idle, which is normal I understand. Once underway and for the few minutes after WOT brought back down to idle it does not smoke. My issue is that once it cools down and idles it begins to smoke and thats a problem because I troll a lot. This outboard is on a jon boat so the motor is practically right next to me when Im driving. So, my question is, I want to run an oil mixture of say 70:1 or 80:1 to mitigate the smoke while trolling, what oil will provide the best protection at a higher fuel to oil raito? Before anyone gets into the mixture screw conversation I will say I have spent plenty of time adjusting it and it is set PERFECTLY and runs excellent. Current oil is Penns tcw-3 semi synthetic @ 50:1. Again, minimal smoke but once the motor cools for a few minutes it begins to smoke at my 2mph trolling speed.

Idle mixture a bit rich maybe? Every two smoke I've had will give off smoke signals if you let it run low speed long enough, but the ones that really puffed were because they were a tad rich. Before you start playing with oil mixes, maybe try setting the idle a bit leaner (usually clockwise or "in") and see what happens.

 

[Cujet]

You chose a good oil, but there may be other oils that could potentially produce lower smoke levels. SeaDoo XPS oil was an interesting product that worked well and was relatively low smoke. Of course any EG-D rated oil is a low smoke product and will provide as much protection as any oil available at 80 to 1, which is to say, not ideal.

Some trolling guys find that 100% synthetic oils are lower smoke.

However, I suspect that the engine is simply not running at an ideal temperature when at idle, and the result will be smoke with any oil choice.

 

[JTK]

Have you tried any other quality, name branded marine 2-stroke oils to see if they make a difference?

The only little 2-strokers I've used that didn't puff clouds at idle were ones like a Tohatsu 9.9 that only has through-prop exhaust. No exhaust ports above the water line.

 

[1978elcamino]

Have you tried any other quality, name branded marine 2-stroke oils to see if they make a difference?

The only little 2-strokers I've used that didn't puff clouds at idle were ones like a Tohatsu 9.9 that only has through-prop exhaust. No exhaust ports above the water line.

No, I have not yet tried another oil because I'm still using what is left in my three gallon tank. I have some maxima Super M that I use in my sons dirt bike. I may mix up a gallon and give that a try. However, you brought up a good point about the Tohatsu, I wonder how it would be if I made a plug for the port in the exhaust housing to plug it up while trolling. That would force the exhaust out the prop during idle. Hmmmm, Im going to work on that.

 

[vw7674]

any Maxima oil will be 3x cleaner than a big national brand.
Maxima 927 is my favorite, it does smoke the least. And the scent is like buttered popcorn.

 

[1978elcamino]

any Maxima oil will be 3x cleaner than a big national brand.
Maxima 927 is my favorite, it does smoke the least. And the scent is like buttered popcorn.

And with Av Gas or VP, Castor smells like Heaven!

 

[Rand]

try different tcw-3 rated oil.
some are worse than others.

 

[Tman220]

I have a 1975 Johnson 9.9 and a 1981 Evinrude 15, same basic engine that you have with different ignition components, so I have a pretty good idea of how these things operate.
First of all, you mentioned you have adjusted the mixture screw, which is definitely important to get right if you spend some time trolling. Another aspect which affects low speed performance and trolling quite a bit is the proper engine temp. Have you changed the thermostat or checked idling temps?

With a fresh thermostat at low idle you should be seeing 145-150 degrees on the top cylinder right below the end of the flywheel. With a 1991 it's not far fetched to be 31 years old, rusted, and now defective stat.
With that being said I can operate either of these outboards and trolling speeds, burning 50:1 for hours without a ton of smoke, and the loading up is only noticeable when accelerating.

I know some people recommend fuel oil mixture leaner that 50:1 if you spend all your time trolling but certainly increases engine wear when running at higher speed. I wouldn't lean out the mixture as a first resort, but as a last resort. Check that thermostat first.

 

[oilcandave]

As above...heat at idle and slightly above is your friend. Thermostat on that model is easy to replace if needed. 140-150f at low speed is correct. I run 32/1 on mine with little smoke...there should be some smoke though. I can only put my hand on the thermostat for 2 seconds or less at trolling speed. The 74', 75' and 76' years ran on thermostat at all rpm ranges. The later years as rpms increase the water bypasses the thermo as the thermo is held by a calibrated spring.

 

[1978elcamino]

I have a 1975 Johnson 9.9 and a 1981 Evinrude 15, same basic engine that you have with different ignition components, so I have a pretty good idea of how these things operate.
First of all, you mentioned you have adjusted the mixture screw, which is definitely important to get right if you spend some time trolling. Another aspect which affects low speed performance and trolling quite a bit is the proper engine temp. Have you changed the thermostat or checked idling temps?

With a fresh thermostat at low idle you should be seeing 145-150 degrees on the top cylinder right below the end of the flywheel. With a 1991 it's not far fetched to be 31 years old, rusted, and now defective stat.
With that being said I can operate either of these outboards and trolling speeds, burning 50:1 for hours without a ton of smoke, and the loading up is only noticeable when accelerating.

I know some people recommend fuel oil mixture leaner that 50:1 if you spend all your time trolling but certainly increases engine wear when running at higher speed. I wouldn't lean out the mixture as a first resort, but as a last resort. Check that thermostat first.

I have actually thought about the Tstat and low RPM heat a possibility of what is causing the smoke. I will get my heat gun out this week and check next outing, great idea. As for the mixture screw, its absolutely correct. My previous boat had a Suzuki EFI 2t, it smoked a lot when cold but after the engine got to temp there was very little smoke the rest of the day. I actually removed the stats on that motor a year after it was new in 2002, it never ran better.

 

[oilcandave]

..put the thermo in pot of water..heat while monitoring the water temp with thermometer.

 

[repairman54]

Full synth. oils are lower smoke. I'm using Klotz in all my 2 smokes since I buy it by the gallon for snowmobiles.
I would not run that old outboard at less than 50:1 mix.

 

[Slick3914]

Try Amsoil 100:1

 

[1978elcamino]

I will take a look at the tstat this weekend

 

[Warlord]

Don’t be trying to troll with any of the dirtbike oils mentioned. They’re meant for high rpm/high temps which is the exact opposite of trolling conditions. Use a proper tcw3 oil. It’s going to smoke a little bit no matter what but you can choose an oil with a more pleasant aroma to make it less offensive. Even my whiz bang etec smokes and smells a tiny bit when trolling if the wind is just right and it’s probably running at some ungodly lean ratio. Have you tried dragging a bucket behind so you have to run a bit higher rpm to achieve the same troll speeds?

 

[FZ1]

Quick Silver is a good tcw3 blend available at Academy. Not overly smoky in my 9.9 Rude. Omc did testing with 75 and 100 to 1 oils and they ran slightly better than 50, but, Omc was concerned with the wear rete so they spec'd 50. Best not to go much higher. Ymmv

 

[super20dan]

bring 2 gas tanks. one at 50/1 for high speed and one at 70/1 for trolling.