re: just bought a used boat

You may not be able to do this because it does not idle, but it's worth a shot to tell you.
Google "Shock Treatment with Yamalube Ring Free"
Basically you'll need to know exactly how much gas is in your built in tank and mix accordingly, or do what I did and use a two gallon external can.

My procedure for oil injected 2 stroke engines:

• You’ll use 2 oz of Ring Free per gallon of gas. Some will tell you to use seafoam, etc, but to me Ring Free cleans better (30% is proprietary ingredients)

• To use a remote tank you’ll need to also buy a secondary primer bulb and hose.

• Take the engine cover off and follow your incoming fuel line and find the hose splice before the fuel filter. Tap into the fuel line there with the new hose and primer bulb, should be exact matches in size.

• Mix 2 gallons of gas with 4 oz of ring free and place the tapped in fuel line into the satellite tank and prime the “new” fuel bulb/hose to the engine.

• Start the engine on the garden hose in your yard and let it burn ½ to 1 gallon of the Ring Free mixture.

• Shut off the engine and let it sit for a few hours.

• Run it again and burn another ½ to 1 gallon of the mixture again.

• Let it site for a few hours.

• Disconnect the tapped in hose, reconnect to your original fuel line, prime it back again and run for 15 minutes or until you are sure you you’ve run all the ring free mixture out.

You will have to put oil in Ring Free mixture if your 2 stroke is not oil injected!

This should clean your entire engine fuel system and can be done when you are sure there is not another fuel issue upstream of your outboard. I.E. water in your fuel tank, etc…

Then change your plugs and fuel filter.