milky oil spraying out from behind prop

[Cooper23]

don't laugh, first time posting to ANY forum...
i started up my 1980 15 hp Evinrude and while it was running in gear i noticed a milky beige fluid being sprayed off the blades of the prop. on closer inspection it appears to be coming out from behind the prop, only when it spins. not if it sits idle. I drained the gear case and that fluid was nice and black no water at all. is this beige stuff leftover oil from combustion? could it be leaking out of the gear case? into the prop shaft/exhaust area?

 

[thx997303]

Re: milky oil spraying out from behind prop

I actually wondered the same thing. I was told it was normal, but I am still unsure.

 

[CATransplant]

Re: milky oil spraying out from behind prop

That stuff is oil, mixed with water. The exhaust comes out the center of the prop, and carries the cooling water, plus unburnt oil. That's the frothy stuff. When the prop's spinning, centrifugal force (or is it centripital?) carries it out on the blades, where it gets flung off the end.

Nothing to worry about.

 

[jtexas]

Re: milky oil spraying out from behind prop

centrifugal, as far as I know, CA, but I've been told that it's not a "force" at all, just the result of compliance with one of Newton's laws (momentum or some such); of course, I have no formal training in any kind of physics.

anyway , I agree long as there's no water in the gearcase, you can safely conclude that it is in fact unburnt engine oil, not at all uncommon. Or maybe the result of carbon build-up. check out the "decarb" thread in the engine FAQ section for an excellent writeup on how to deal with the situation.

If your gear oil is black, then very likely it's been in there too long, or maybe the wrong oil. Most marine gear oils nowadays are amber, and get darker the longer you don't change 'em. Marine oils are formulated to retain their viscosity in the presence of water...change it every year (I do it in the fall before the first hard freeze, so in case of water intrusion it won't crack my gearcase open). Of course, maybe the last guy just used a black marine gear oil........

 

[jmendoza]

Re: milky oil spraying out from behind prop

Drain the gear case, re-fill with OMC Sealube and be sure to use new nylon seals on the fill and vent plugs, and be sure to tighten them well. Pressure test, or have your local marina pressure test, and if it passes, put in the vent plug, tighten it real good and you should be fine.