8HP Merc (2003) leaking oil from prop shaft

[foggysail]

Several years ago I purchased a used 8HP Merc outboard from a friend. The engine had less than 10 hours on it when I purchased it. After using it for about a month, the lower unit gear oil started to leak from around the prop shaft.

That winter, I purchased the special tool ($75) needed to remove the shaft from the lower unit along with new oil and water seals plus a new water pump kit. Put everthing together and before the end of last season, the thing started leaking again. This season it is leaking so badly I am going to put my old (20years) standby Yamaha back onto my boat and take the Merc home.

I see other Merc's with the same problem! I don't know the history of others here on the board with these engines but I for one am complete disgusted with this engine. My intentions are to rip this junk apart one more time and measure the seals and replace them from a seal manufacturer rather than purchase another substandard set of seals from a Merc parts distributor.

Are others having a similar problem? How did you solve it? this engine has less than 25 hours on it. JUNK!!!

Foggy

 

[SeaKaye12]

Re: 8HP Merc (2003) leaking oil from prop shaft

Hi,

I guess you're certain that it is in fact gear lube that you're leaking? My 15hp Johnny oozes oil residue from the powerhead if I idle (troll) for extended periods. The ooze looks alot like gear lube. I've read here that because of incomplete combustion in the older 2 strokes; oil exits through the exhaust (the gas either burns or evaporates; leaving the oil...)

Anyway; hopefully someone more experienced than me will come along soon and help you further.

Good luck and thanks for reading, Chuck

 

[foggysail]

Re: 8HP Merc (2003) leaking oil from prop shaft

Thanks Chuck for responding.

MAJOR EDIT:

After reading Chuck's post and a night's sleep, I asked myself if my problem could be unburned oil? I am going to pull the prop on my next trip to the boat so I can see exactly where the oil is leaking. I still think it is from a seal but there is nothing like being sure.

The one think that makes me want to pull the prop is I burn a mixture of 25:1 rather than 50:1. I never had a problem with the Yamaha with this mixture and always believe I would be better off with overlubing rather than under lubing.

More later--

Foggy

 

[SeaKaye12]

Re: 8HP Merc (2003) leaking oil from prop shaft

I usually run WOT for a minute or so before returning to the dock. Seems to blow the snot out of it and leaves less of a mess on my garage floor...

Chuck

 

[foggysail]

Re: 8HP Merc (2003) leaking oil from prop shaft

WOW!!!! How time passes by but this thread needs an answer.

Seakaye12 PUT HIS FINGER RIGHT ON THE PROBLEM!!! Yup! I had ordered seals, pulled the engine apart as noted in an earlier post and the thing just drippppped oil all over the deck.

I stopped pouring oil into the gas for mixing and started measuring the amount added. Guess what! The engine runs smoother and NO MORE OIL dripping on my deck.

I would have replied much earlier but I lost where I posted my question.

Foggy

 

[blandes]

Re: 8HP Merc (2003) leaking oil from prop shaft

What do you mean by measuring? Are you mixing your gas/oil in a seperate container then pouring it in the tank?

Thanks - have the same problem

 

[emckelvy]

Re: 8HP Merc (2003) leaking oil from prop shaft

Sounds like he wasn't mixing his oil very precisely with the fuel. 25:1 is way too much oil for a modern motor. Just stick to 50:1 with a quality TCW3 oil.

And just for future reference, it's not uncommon to see an oily discharge from around the prop. Just as the previous poster stated, if it smells gassy or fuel-y, it's coming from the motor.

If the discharge stinks like sulfur, that's gear oil. You're smelling the EP (Extreme Pressure) anti-wear additives in the oil.

The best way to confirm a leaking gearcase (in the absence of a puddle of stinky gear oil on the floor) is to pull the gearcase oil drain plug. If it's clean oil or even black in color, you're good (change the oil if it's black!).

If you get water out of there or see an emulsified milky mixture (usually like a grey or brownish milkshake) you've got water intrusion problems.

The most typical reason for water in a lower unit is from leaking oil seals around the driveshaft. The suction action at the base of the water pump draws the oil right out of the gearcase and it's immediately displaced with water.

Shift shaft seals can leak also, usually a much slower leak and you'll see oil on the floor if you leave the motor tilted up.

Propshaft seals sure can leak and you'll see a puddle of oil. The water intrusion into the gear oil may be slower than what you'll get with leaky driveshaft seals.

Anyway, HTH & glad things worked out............ed

p.s. all that extra oil in the fuel will cause carbon buildup, be sure to decarbonize that motor as per this posting:

http://forums.iboats.com/showthread.php?t=158076&highlight=seafoam