I bought a boat that was 10 years old. Had no idea of how well the old owner maintained it, and service department at his marina was clueless. I wanted to replace whatever 2-cycle oil he had on board with full synthetic 2-cycle Injector oil.
I used a suction gun to suck out whatever oil came out of the big storage tank, and eventually got to the bottom. Then it got ugly - brought up big chunks (yes, chunks) of blue-green Jello. There was about a 1/2" layer of this stuff on the bottom of the tank, and some of it found it's way up to the smaller reserve container that sits on the engine.
Removed the big tank and rinsed it with gasoline to get the sludge out. As far as the little tank on the engine, I drained it the best I could, then I had some conventional 2-cycle oil that I poured in to the little tank, mixed it up with the sludge, then let it drain. Repeated this part 4 times until all the sludge was gone from the little tank. Only used about a quart of oil for the whole process. Might want to take a look yourself if you haven't topped off your big oil tank yet.
I used a suction gun to suck out whatever oil came out of the big storage tank, and eventually got to the bottom. Then it got ugly - brought up big chunks (yes, chunks) of blue-green Jello. There was about a 1/2" layer of this stuff on the bottom of the tank, and some of it found it's way up to the smaller reserve container that sits on the engine.
Removed the big tank and rinsed it with gasoline to get the sludge out. As far as the little tank on the engine, I drained it the best I could, then I had some conventional 2-cycle oil that I poured in to the little tank, mixed it up with the sludge, then let it drain. Repeated this part 4 times until all the sludge was gone from the little tank. Only used about a quart of oil for the whole process. Might want to take a look yourself if you haven't topped off your big oil tank yet.