brown sludge coming from behind prop...

[fishouttawater]

Hello. I've a 1996 40hp Mariner (4cyl/2 stroke) which came with an old but straight 89 Sea Nymph 170SC which I got several weeks ago. I spent 5 or so hours slowly trolling yesterday, and today after work as I was tinkering (compulsively!) I noticed a small puddle (less than an ounce) leaking from where the prop goes on the shaft. It's a very sludgy and gloopy looking stuff, kind of the consistency of thick custard but but stratified with different rusty brown colours.

A post in 2008 describes a similar problem/issue but after an oil change there were no follow ups so I'm unsure if that member solved his problem. Does anyone have any thoughts as to the cause of the problem? I'm sure it's a seal on the shaft somewhere but would like some confirmation before I roll the sleaves up. (I have a manual and am reasonably mechanically minded as long as electrics aren't involved)

Thanks

Fishouttawater

 

[jake505]

Re: brown sludge coming from behind prop...

sounds like the seal is leaking but you could always just pull the prop to see where it is coming from. shouldn't be to difficult to take the prop off

 

[nauti thoughts]

Re: brown sludge coming from behind prop...

Have the same sludge coming out of mine, talked to a guy and he told me before i replace bushings and tear into it, to make sure you are running good oil, weather it be Merc, or Johnson just no hardware store junk. Just drained 5 gals of gas to find out. Figure it is worth a try

 

[fishouttawater]

Re: brown sludge coming from behind prop...

OK. Pulled the prop off, but couldn't remove shaft as I needed a tool to undo a spindle nut which seems to hold the gears,etc. Drained the LU oil and it was fine - a reasonably clear dark green. The sludge pools up in the void behind the prop and gear housing.

I assume its making its way their via a leak in one of the seals - but It doesn't seem to be too severe. I think the sludge is an emulsion formed with the gear oil, some exhaust and water - very tasty.

Anyway, I've replaced the LU oil, cleaned up the sludge and replaced all parts. I guess I'm ready to go but will keep an eye on it to gauge the extent of the leak. By the condition of the old LU oil, which didn't seem too bad, I don't think water is working its way into the gearbox....yet. I'll keep posting updates over the next little while. The photos show what I've been looking at.

Thanks for all comments and help.

Fishouttawater

 

[corm]

Re: brown sludge coming from behind prop...

Hi,

That's normal unburnt oil draining out of the exhaust housing.

 

[fishouttawater]

Re: brown sludge coming from behind prop...

Just checking in again.

Been out several times since and only notice the sludge after an extended period of trolling. I assume slow trolling concentrates or increases the mix of exhaust and water to create the sludge. Nothing to worry about (always feel nervous saying that!)

Thanks for the help and happy fishing/boating to all.

FOW

 

[corm]

Re: brown sludge coming from behind prop...

Hi,

You are correct. it is just unburnt oil drool, water, and carbon from you exhaust housing. Normal stuff. Use a name brand TC3 rated oil for best results.
If you give it a good hard run at the end of the day you will help clean that drool out of the exhaust housing. A 1/2 mi or more of WOT helps mine stay clean at the end of the day