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Help! I ran straight gas in my 2-cycle outboard :(

H

Hefner

New member
So I just purchased my first outboard boat motor. It’s a 9.9hp 1997 Mercury. I should have known better but didn’t realize I needed to run 2 cycle gas. So I ran it for about 15-20 minutes total. Mostly at a medium-low idle speed. I revved the engine a couple times during this process. It ran fine throughout and it didn’t stall/seize. Well, my neighbor stopped by and we were talking and I realized my error. So my plan at this point is this... drain the present non-mixed gas and fill with proper mix. I also purchased a valve pressure test tool to see if I’ve lost pressure. Any other recommendations? Thanks!
 
I believe you can remove some covers on the side of the 2 stroke blocks.----Lets you see the pistons and rings.------Hard to believe it could survive 15 minutes of this treatment.
 
racerone said:
I believe you can remove some covers on the side of the 2 stroke blocks.----Lets you see the pistons and rings.------Hard to believe it could survive 15 minutes of this treatment.
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Thanks, I will take a look to see if there is side access. Appreciate the recommendation.
 
Drain the gas, refill with 50:1 and go boating.

I heard of a guy who ran most of the summer, pulling water skiers, occasionally and accidentally, without oil in the gas all the time. Motor was worn out but still running.

jeff
 
fastjeff said:
Drain the gas, refill with 50:1 and go boating.

I heard of a guy who ran most of the summer, pulling water skiers, occasionally and accidentally, without oil in the gas all the time. Motor was worn out but still running.

jeff
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Thanks for the reply. Fingers crossed I dodged a bullet. If I drained it and refilled and ran it... would I possibly do more damage requiring a bigger repair job than I could have on my hands now?
 
Inspect as per post # 2.---- Or squirt an ounce of oil into the carburetor.----Mix gas and oil in the tank and roar down the lake.---Hope for the best.
 
racerone said:
Inspect as per post # 2.---- Or squirt an ounce of oil into the carburetor.----Mix gas and oil in the tank and roar down the lake.---Hope for the best.
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Thanks. My friend recommended removing spark plugs and putting a few drops of the oil directly inside. What do you think?
 
Stand the motor carb facing up throttle wide open and pour 5oz of oil down it and let it run out of the open plug holes. Pull it over a few times to drive the oil out of the holes then install the plugs and start it.
 
racerone said:
I believe you can remove some covers on the side of the 2 stroke blocks.----Lets you see the pistons and rings.------Hard to believe it could survive 15 minutes of this treatment.
Click to expand...
Thanks again racerone. I finally got a break from work to take a look. There was a side cover, allowing me a great view of the pistons / rings / far half of the cylinders. Great news is that it looks nice and smooth inside. No damage that I can see to the cylinder walls or the pistons. There even seemed to be some residual oil still on the pistons as I turned it over some.

Quicksilver said:
Stand the motor carb facing up throttle wide open and pour 5oz of oil down it and let it run out of the open plug holes. Pull it over a few times to drive the oil out of the holes then install the plugs and start it.
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Thanks Quicksilver. I didn't see your post until this evening after reassembling the cover etc. Before putting on the cover, I went ahead and put about 0.2 cc of my 2 cycle oil into each cylinder to add a little extra coating to the cylinders. But that won't get to the bearings, etc. So if I understand correctly, if I go ahead and add the 5 oz of oil to the carb and turn it over a few times, the oil will coat the bearings, etc and move past the piston and out the open spark plug holes?
 
Mix a gallon of gas at 24-1 and start it on that. How much mixed gas was in the tank before you added to it? If you ran your motor on straight gas no amount of oil is going to save it.
 
flyingscott said:
Mix a gallon of gas at 24-1 and start it on that. How much mixed gas was in the tank before you added to it? If you ran your motor on straight gas no amount of oil is going to save it.
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I was starting to get my hopes up too much then? I'd guess only had less than half tank of mixed and I added a about 2 gallons of straight. Let's hope it was really rich before I added the straight. I was hopeful after seeing the decent state of the cylinders and some residual oil on the pistons. But we'll see. I reassembled yesterday but I've been at work solid til Saturday. So Saturday I'll try to run it. I appreciate the input from everyone. I've called a couple mercury mechanics in my state also. They said to just run it with mixed and call it a day, but I'm hoping to maximize my success and avoid further damage. So still contemplating pushing the 5 oz of oil thru as quicksilver suggested. I am up for trying anything.
 
You must always be mindful on the gas mixed with oil situation; my Merc 2 stroke is oil injected; I drain my carb bowls at the end of the season to prevent gumming them up because sometimes I do not use the boat for a few seasons; hence, when I start it up for the first time in a new season, I squeeze bulb a 50:1 mixture into the empty carb bowls and start it that way; then, I connect back to the pure gas main tank.
 
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