just purchased a 04 seadoo gti le. looks like he was using mercury 2 stroke oil in it. Any reason I couldn't go to synthetic like either the xps or quicksilver.
You have to get that oil out no questions asked.
Drain the tank and vacuum as much out as you can from the 12mm rotary cavity lines. Replace the oil filter and fill with any full synthetic API-TC only oil. Do not use any dual rated oils or anything that says TCW-3 or 2 anywhere on the label.
That oil will ruin the engine.