Yamaha 650 JetSki smoking... forgot to add oil. Whoops! HELP! :)?

Question

Hi! I bought a 1990 Yamaha 650 Waverunner, filled it up w gas like my SeaDoo and didn't realize that the Yamaha need 2 cycle oil mixed in w the gas. So. I put it in the water, it started ran really slow and smokes. I realized the problem and put as much oil as we had straight into the gas tank and shook the waverunner in the water. It was about 12 ounces for 6 gallons of gas which is about 4 ounces short I believe. Still smoked and ran slow. I've since gotten it out and not started it, but I'm sure i would still start so I didn't kill it just yet. It maybe ran for 30 minutes? Any ideas of how I should proceed? Help please! I'm obviously a beginner when it comes to jetskis. Thanks for any help!

Answer 1

The tank probably had some premix in it already, so it wasn't exactly straight gas, right?  If it smoked soon as you started it, that tells ya right there it had oil in it.

the recommended ratio is the max needed for all out WFO operation, it requires a good bit less for low RPMs

compression test will tell whether you caused any damage.

Answer 2

You may have too much oil.

That machine does use 2 stroke oil, but it came equiped with a tank and injection system. It should mix the fuel automatically.

First determine if the oil injection has been removed or not, then check the plugs to see if they are oil fouled.

Answer 3

If you only ran it for a very short time without oil the problem probably is not with the oil mix but a carburetor problem. If you run the engine without oil it will burn the piston rings and piston walls.  Sounds like this needs a mechanic to fix tour problem.  You might try replacing the fuel with new gas, with the right mixture, first.