I posted this a few months ago, but it still has me concerned.  The motor has not been in the water since I noticed the problem. Its an '83 50hp Merc. I pulled the LU oil and it was goldish color with no water, while the stuff leaking out of the prop is black/dark brown.  

  I called an OB mechanic today and told him what was going on.  I told him I thought it was a bad prop seal.  He said right away that since each "substance" was of different color that I have nothing to worry about.  Its just caused by the exhaust of a 2-stroke motor.  He suggested that there was nothing wrong at all.  Also he said that the first time I go out, when I'm done, check the LU oil to make sure there is no water.  That's it.

 Just wondering what you guys suggest as to what would cause it to look like this.  I always trim it down to drain the water when I'm done each time, but then trim it up and add my transom saver to trailer it.  Its stored covered (boat only) outside with the motor trimmed up.  

    When it rains could water collect in the prop and mix with old exhaust to cause this?

Thanks!

NO!!!!  I would check the lower unit seals.

That's a lot of oil there.  I think I'd have that checked out.

That's a lot of oil there. I think I'd have that checked out.

Not an expert here... but I agree!!!  That is a lot of oil!!!  Have the engine checked out!!!

I agree as well.  I need to pry have it checked out.  I couldn't believe what the mechanic said.  One more question though.  Why would the oil be two completely different colors?

The LU oil looked very normal and far from that black/brown color dripping out of the prop.  Also there were no signs of water in the LU when I drained it.  The total oil lost was pry <1oz.

Thanks again!

If the lower unit lube is not low, and there is now signs of water in then it's probably from letting the motor idle a lot before loading. If you have to go very far in a no wake zone to get to the dock/ramp and then have to idle around while loading the boat, it's very feasable that is engine residue.

If you are still running the oil injection hooked up, then it's highly possible, Those old merc oilers could really pump some oil at idle, and smoke like and old coal burning locomotove after they idle for a bit.

One note, you should never store a boat with the motor trimed up, too many places it can keep water traped and could cause you some major grief if allowed to freeze in there.

Posted by: Way2slow      Posted on: Today at 7:04pm

If you are still running the oil injection hooked up, then it's highly possible

It doesn't have oil injection, and I usually run about 45-50:1 with gas/oil.

Posted by: Way2slow      Posted on: Today at 7:04pm

If you have to go very far in a no wake zone

LOL, that is pry my problem, 90% of my lakes I fish are "no wake" lakes.

One note, you should never store a boat with the motor trimed up, too many places it can keep water traped and could cause you some major grief if allowed to freeze in there

I'm sorry, I didn't say this earlier, I do store it in a heated warehouse over the winter.  Would it still be wise to store the motor trimmed down when I store it outside in the summer?

The oil is coming out the real seal, its burnt because it all leaked out and was getting the lower unit hot .

Thats what it looks like to me, my 10hp just did the same thing once i got it going. And had it happen on my old 40hp years back as well, just be glad u caught it before damage occurred.

Just out of curosity did you check the plugs to see how much oil is on them? If it blowing out the exhaust then it would also be fouling plugs real bad.  But guess would be that it is coming from the seal in the lower unit.

There is NO WAY that is caused by exhaust.  have that checked out pronto!

Yeah, I'm going to call tomorrow to have them take a look at it.  I just know there is something wrong, it never did it all (last) summer until the last time I WAS gonna go take it out.  That is when I noticed it.  Lets just say that fishing trip was ended before it even thought about getting started.  I'll keep you guys posted as to what was the real problem with the oil leak.

Thanks for all the advice!!!

Seen it buches of times on my motors and can assure you they don't leak.  If it's full of lube and no water, where did it leak from??.  After all, the LU is the only thing down there that has an oil reserve.  Still looks more like unburned fuel/oil from exhaust residue to me, but since I know nothing about them, what would I know.

Level the motor, take the top plug out and check the lube level, or haul it to a shop and pay them $300 -$500 to replace what might be prefectly good seals.

Posted by: Way2slow      Posted on: Today at 10:16pm

since I know nothing about them, what would I know.

LOL, I totally respect and value your opinion!! Way2Slow says its good, its good enough for me.

Again, Thanks for all the help!!!

were no signs of water in the LU when I drained it.  The total oil lost was pry <1oz.

Thanks again![/quote

I missread this and thought he said there was only  1 oz of oil LEFT in it.

My mistake.

mine looks like that after I idle it on the hose for any length of time, and when I fish a certain lake that has a 1 mile long idle only speed. Its not lower unit oil. Touch it and smell it, it'll smell like combusted gas I bet.

I took mine over the mechanic today. I had dark smelly oil-ish looking stuff SORT of like that. Mine is exhaust, so some of that could be exhaust. The motor burning too rich, idling all day, plugs wrong (in my case the plugs in the motor were automotive plugs and not marine plugs too). Next fill up I will run mid grade and open it up for a while, since I don't run and gun either. Do you know what your plugs are?

I was pretty happy to say the least. I bet it's not something you would expect.....let us know.

I would have a mechanic inspect the lower main seal on the crankcase.

If the seal is worn, you will get seepage from the crankcase.

In addition, water will also begin to destroy the bottom bearings.

A quick way to check this is to put a rag over the lower carb opening

to stall the engine.If the RPM's pick up, it is pulling air from the seal.

Posted by: BD      Posted on: Mar 22nd, 2007, 6:54pm

Do you know what your plugs are?

No, I don't.  I have had the boat since last april. I probably should change them out.  What do you guys suggest for plugs?  Also what do I need to gap them to?  The motor is an '83 50hp Merc.

As far as the motor goes, I'm gonna take it out on saturday and run it for a while.  After I'm done I will drain the LU oil and check for water, if there is none, I will refill with new be on my way, if there is water, its off to the mechanics shop.