Used wrong oil in 2 stroke - will it cause serious damage?

[ortho85]

I made a stupid mistake.

I have a 6 year old 75hp Mercury 2-stroke outboard. I had it serviced recently, then on my first run after that the low oil alarm sounded. I refilled the oil, but when I was cleaning the boat up (it sits in a canal on the water) I noticed that the oil was 4 stroke! The 5 litre bottle was about empty, so I must have been using 4 stroke for a while.

Now the engine is a little hard to start, runs perfectly, but tends to stall at idle. It's been run about 3 hours since discovering the error.

Can I do anything simple to fix my stupidity, or do I need professional service?

I have bought some 2-stroke fuel system cleaner. Do I need to do anything else? BTW I'm in Australia - I have seen recommendations for 'Seafoam' but I can't find it here.

Thanks.

 

[tpenfield]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

If you Google "4 stroke oil instead of 2 stroke" a few things come up.

It is going to foul the plugs and gunk everything up inside the engine. . . severe damage, no, but more changing spark plugs, and you might want to do a crankcase and combustion chamber flush . . .

Put that on the "don't do it again" list :joyous:

 

[Don S]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

Empty the reservoir, refill with the correct oil, and run some Power tune through. Should be fine.

 

[Texasmark]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

and run some Power tune through.
View attachment 177448

Or Sea Foam would be my suggestion. It was initially made to decarb outboards, i.e. clean up combustion deposits in 2 stroke engines. They recommend 1 oz per gallon of fuel/fuel-oil mix (whichever you use). For the 16 oz bottle, I'd double up to 2 oz per gallon.

HTH,
Mark

 

[mr 88]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

That all we ran in the 50's and 60's,those engines are still around,1 quart of 10-30 to 6 gallons and we were good for 1/2 the day.No cleaning anything,just ran it.

 

[wired247]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

Clean your plugs . It will be fine. 2 cycle oil just burns off cleaner than 4 stroke oil. 4 stroke oil probably does a better job of lubricating anyway.

 

[Silvertip]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

That all we ran in the 50's and 60's,those engines are still around,1 quart of 10-30 to 6 gallons and we were good for 1/2 the day.No cleaning anything,just ran it.

That's because many of those older engines had sleeve bearings, not needle and roller bearings as they have today. You also changed plugs and had carbon issues much more than today. Regular engine oil is not designed to "burn". Two stroke oil is.

 

[ortho85]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

Thanks for all the replies. I feel better now!

And Merry Xmas (tomorrow) from a hot Brisbane - 30 Celsius today - 86 in your language.

Cheers!

 

[Texasmark]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

That all we ran in the 50's and 60's,those engines are still around,1 quart of 10-30 to 6 gallons and we were good for 1/2 the day.No cleaning anything,just ran it.

Well sir, I remember running 30 wt straight viscosity at the quart to 6 gallon ratio as multiviscosity didn't exist at the time. My favorite brand was the red can of Amalie (Pennsylvania) motor oil "Amalie, better than it has to be" was their slogan. With all that oil and a low voltage ignition system, when compared to the high voltage CDI systems of today, and no thermostats, I am amazed that those old suckers ran as well as they did. Ha!

Mark

 

[wired247]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

two stroke oil does two things better than four stroke oil. It mixes with gas better and it burns cleaner. Running four stroke oil for short periods isnt going to hurt a thing except for gumming up the plugs. My Ford truck burns four stroke oil quite effectively and the plugs are still the original 115,000 mile units.

 

[Texasmark]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

My Ford truck burns four stroke oil quite effectively and the plugs are still the original 115,000 mile units.

Yeah but your Ford is a 4 cycle and has a crankcase unlike a 2 cycle which has to lube via the gas.
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While we are on the subject, I was viewing you-tube yesterday and a guy was running a '58 Johnny 10 hp (in pristine condition) and I was amazed at the lack of smoke. Nobody mentioned the fuel oil mix he was running but I recall them smoking a lot more than that in the day.

Mark

 

[Bamaman1]

Re: Used wrong oil in 2 stroke - will it cause serious damage?

I think that outboard motor oils are essentially 20 weight non-detergent motor oils. I'd suggest changing the plugs and running an additive like SeaFoam through the fuel system. You'll probably be okay.