Fluid leaking behind prop (pic inside)

[curapa]

What is the deal? Is there a seal that needs to be replaced?

 

[ezeke]

Re: Fluid leaking behind prop (pic inside)

Most likely unburned fuel/oil mix draining from the engine, and normal.

See: http://forums.iboats.com/showthread.php?t=207285

 

[curapa]

Re: Fluid leaking behind prop (pic inside)

Thanks Ezeke, I just painted the engine white and I never noticed it before. I checked the gearcase oil and it was fine.

 

[neilpryde]

Re: Fluid leaking behind prop (pic inside)

Don't want to start a new topic because of similar problem/question.

Just bought the boat and engine last week. We had to came back over a speed restricted canal (so low rpm) for 15 minutes. Drove back home with boat and engine on trailer for about 2 hours.

At home found some oil leaking at the prop (only there). Happily i found this thread and read also the info from JB. So most probably it will be unburned oil because of low RPM before shutting engine down. To me the oil seems quite dark in color.

If I leave my engine unused for let's say the next 4 weeks. Is it correct if i conclude that, when oil is still leaking after 4 weeks, the problem would be a sealing problem and if oil leak has stopped, it was most probably unburned oil? I am looking for an easier way then servicing the whole lower unit for (maybe) nothing. It's also my first engine, so i might be a bit overscared. I bought the OEM manual, so if needed replacement can be done.

The previous owner did change the lower unit oil last year and didn't found any evidence of water protrusion.

Engine is a 1998 Johnson 35HP 3 Cyl 2 Stroke with less then 100 hours.

Anybody that can see on the picture (oil color) which oil is leaking (lower or engine oil)?

 

[F_R]

Re: Fluid leaking behind prop (pic inside)

You have to realize that every drop of oil that you put in the gas passes through the engine. Some of it is burned (smoke) and the rest goes out the exhaust. As it passes through the exhaust chambers, it picks up particles of carbon that turn it black. Guess what? The exhaust outlet is the hollow propeller hub.

When you are running at idle, there is less oil burned and more going out the exhaust. So you are more likely to see it after a long slow run. It can take days or even weeks for it all to completely run out.

However, you also could be continuing to let fuel seep through the system if you don't disconnect the fuel tank hose when in storage.

 

[neilpryde]

Re: Fluid leaking behind prop (pic inside)

Ok thanks! So your guess is the unburned oil as well. Makes me more comfortable.. It's not fun to find some leaks on an engine you just bought. But it will be most probably nothing seriously.