2 Cycle Outboard Oil

[SMallison]

Need a little help! I was given a 1950s OMC recently. I took it to the lake this weekend to see if it would run but got a little ahead of myself and did not research oils first... I assumed 2 cycle oil was 2 cycle oil and used the stuff I had in the garage for the weedeater. I was later told that I needed 2 cycle marine oil. My question is what damage did I do to my motor. I took it pretty easy but I did run three gallons through it.

 

[kofkorn]

Not the expert here, but for a motor that old, I'm sure that it won't have any issues with the weedeater 2 cycle oil for the small amount you've used. The weedeater oil is rated for a high temp engine, and will leave deposits behind if used long term in lower temp (water cooled) motors. If you were talking about regular 10W-30 or something like that, it would be a different story.

I wouldn't lose any sleep over it. I am certain that you wouldn't have done any damage as long as you had a good 50:1 mix of 2 stroke oil of some kind in there for the amount you used.

Use the marine stuff on the next tank.

Good luck!

 

[cgaengineer]

You'll be fine...

 

[lckstckn2smknbrls]

When new this motor probably used straight 30 weight oil mixed 24:1.

 

[Charger25]

You should be ok. To quote Kelly Johnson ( who designed the SR 71) I like the KISS principle. I've used TCW2 and then TCW3 2 cycle marine oil in all of my weedeaters,chain saws and stuff. Any 2 cycle engine, thats what I use. Heck , I had a craftsman weed eater that lasted 17 years and I am not kidding, STILL have the 1989 craftsman lawn and garden tractor that runs like a champ and I think its because I'd dump in all of my unused outboard fuel in it. Sure the plugs would foul up but i'd just clean 'em or replace them.

 

[Loggerhead Mike]

When new this motor probably used straight 30 weight oil mixed 24:1.

x2

 

[NautiBuoys]

Agree you "should" be ok, but if it were mine, I would not make a habit of it.

Air cooled 2 strokes normally run at much higher temps and rpm than water cooled 2 strokes.
Head temps can reach over 500*F and 10,000 rpm are not unusual. For those reasons, air cooled
oils are far more heat tolerant and higher viscosity than for water cooled applications. But, air cooled 2
stroke oil has a high ash content. They require additional lubrication in the form of this ash but they get hot
enough that burn the ash off with no ill effect. Use TWC-3 in a chainsaw and your lacking lubrication.
Outboards run around 5-6K rpms. They don't get hot enough to burn off the ash if you run air cooled
oil in them, and the result is a chamber full of carbon and junk that won't burn off.

And while it may work, it is a generally accepted practice is to not use TCW-3 outboard oil in any air cooled
2 stroke, including even air cooled outboards.

 

[Charger25]

NautiBuoys » Yesterday, 10:22[/url]"]Agree you "should" be ok, but if it were mine, I would not make a habit of it.

Air cooled 2 strokes normally run at much higher temps and rpm than water cooled 2 strokes.
Head temps can reach over 500*F and 10,000 rpm are not unusual. For those reasons, air cooled
oils are far more heat tolerant and higher viscosity than for water cooled applications. But, air cooled 2
stroke oil has a high ash content. They require additional lubrication in the form of this ash but they get hot
enough that burn the ash off with no ill effect. Use TWC-3 in a chainsaw and your lacking lubrication.
Outboards run around 5-6K rpms. They don't get hot enough to burn off the ash if you run air cooled
oil in them, and the result is a chamber full of carbon and junk that won't burn off.

And while it may work, it is a generally accepted practice is to not use TCW-3 outboard oil in any air cooled
2 stroke, including even air cooled outboards.

Not doubting your knowledge, but how many people have had a weed eater last 17 years

 

[Jeeper]

Its hard to damage a good ol omc! With that in mind just make sure your mix is 24:1 and you'll be fine.

 

[NautiBuoys]

I don't know of any air cooled engine manufacturer (be it chainsaw, weedwacker, Stihl, whomever) that recommends using NMMA (water cooled) oil in their engines and we definitely had chain saws come in the shop that didn't last b/c of using TCW oil.