787 RFI drinking oil.

[Michael Haveman]

I had my seadoo 3d 787 RFI out last weekend and it filled up with water, engine included. I pulled the plugs and blew out the water. I got it running again but now the oil is pumping in like crazy with white smoke coming out heavy from the exhaust. Am I in to replace the whole oil pump or could this be an easier fix?

Any advice would be appreciated.

 

[Cobo351]

I had my seadoo 3d 787 RFI out last weekend and it filled up with water, engine included. I pulled the plugs and blew out the water. I got it running again but now the oil is pumping in like crazy with white smoke coming out heavy from the exhaust. Am I in to replace the whole oil pump or could this be an easier fix?

Any advice would be appreciated.

Mine just started doing the same thing...fills the mag side cylinder with oil. If I understand what I've read correctly it's the crank seals.

 

[Michael Haveman]

Mine just started doing the same thing...fills the mag side cylinder with oil. If I understand what I've read correctly it's the crank seals.

Did you fix yours? I am wondering on the cost of it or how hard it would be to do myself. I have worked on 2-stroke engines but never a seadoo.

Also how does a bad crank seal allow so much oil to go into one cylinder? Wouldn't a blown crank seal just make it run lean? (suck in air). I can't find much information on the situation but ill keep looking.

Thanks,

Mike

 

[mikidymac]

The 787 has a rotary valve that is driven by a gear in the middle of the crank. This area has a cavity in the center of the cases that is filled with oil from the 2 stroke oil tank and sealed from the connecting rod chamber and cylinders by internal crank seals. When the inner crank seals go bad they let the oil in from this chamber and drain your oil tank into the cylinders.

 

[Cobo351]

I haven't yet fixed mine Mike. I'm adding a fuel shut off right before the oil pump to get it through into the end of the season then I'll look into a permanent fix.

 

[Cobo351]

Here's a question maybe someone can answer for Mike and I. If to avoid the crank seal replacement (assuming that's the problem) one was to switch to mixed gas, being that it is fuel injection would the gas and oil mixture lubricate the entire engine?

 

[mikidymac]

No, you can not premix a fuel injected ski as it will destroy the injectors.
Also any seadoo engine with the exception of the 951 uses a rotary valve for the intake timing and it is lubed with an oil bath that has to have an oil supply all the time. If your inner crank seals are leaking on any of these with the rotary valve switching to premix is not a solution to the problem.

 

[Cobo351]

That's good info. What are the odds of oil leaking from the rotary valve into just one cylinder?
Thank you

 

[GTX RFI]

Same thing happen to my Skidoo, my understanding the ethanol in the gas is the reason why they are going bad. Everything I read has the same solution put a shut off value and ride it. Just make sure you turn it on when you ride it.

 

[mikidymac]

IT is very common for just one seal to leak. For a better picture your crank has 4 seals one on the front then one on the front cylinder where the rotary cavity is then on the other side of the cavity for the rear cylinder then finally the rear seal. IF either or both of the inner seals leak you will get oil from the rotary cavity into the cylinders.

The reason they leak is they are 20 years old, things do wear out. The quick solution is a valve to shut off oil from the tank when you are not using it but this is just a band aid. I would not do this for more than a season as the seal and the leak will get worse. The correct fix is the pull the engine, split the cases and get a remanufactured crank with new seals.

 

[Michael Haveman]

Is there any other reason the oil could be pouring into the cylinder? My seadoo never sat just filled with water and after I blew it out is when it happened. As well usually the oil that fills up the bottom end will burn off and it will run good again hence being able to put a shut-off valve. Mine just burned heavy the whole time. Just curious before I spend money on a new engine.

 

[Michael Haveman]

Also will the bad crank result in high compression in the engine both my 3D's are running 170-180 psi. Thanks