Oil behind prop 25hp Rude

[zhaan]

Got a slow oil leak coming from behind the prop on my Evinrude 25hp 1985.

No chance this could be waste oil maybe, or am I looking at a seal or gasket fail?

It hasnt leaked before, and it hasnt been in the water for about 3 weeks, all I have been doing is running it with muffs on while servicing it, no long periods of running.

 

[F_R]

Re: Oil behind prop 25hp Rude

Every drop of oil that you put in the fuel goes through the motor. As it passes through the cylinders, some of it is burned (smoke), and the rest goes out the exhaust. Guess where the exhaust outlet is? You got it, through the hollow propeller hub. So of course there is oil in there.

It could be more than normal because you were running it on muffs. You weren't getting the combustion temperatures hot enough to burn much of it in the cylinders.

 

[zhaan]

Re: Oil behind prop 25hp Rude

I thought as much after realising one of the exhaust ports was in the prop but got a little nervous when the oil appeared between the prop and case, like I said nothing major, very slow and very little, makes sense, thanks F_R.

 

[ab1]

Re: Oil behind prop 25hp Rude

Just a cautionary thing...but when you do get it in the water, check a couple times for water in the gearcase. If a seal is bad, you should see some water start to accumulate there. I had a seal go bad once and it was leaking out of the prop just like unburnt oil...except this one cost me a new lower unit.

 

[rookiedave]

Re: Oil behind prop 25hp Rude

Thank you guys. I am very new to boating, and my out board is doing the same thing. I was also a little concerned. I am running my engine in a drum and also not for very long periods of time. This thread has made me feel a lot better now.
thank you

 

[zhaan]

Re: Oil behind prop 25hp Rude

I also forgot to mention that I am due to clean the carb through as the idle is very 'troubled' and tends to cut out if the primer/choke isnt used to help the engine tickover.

So, the fuel is arriving at the engine, its not being dealt with properly so therefore waste oil is on the increase and having to go somewhere, that somewhere is down, down being down the leg (thanks Newton!).