Oil comming out from behind the prop.94 Mercury 25hp

[Underdog1]

When sitting out of the water with motor in position I have black oil comming from behind the prop. After use and pulled out of the water the black oil turns to a light gray color. As long as the motor is in position the leaking contunues. I have been told that I need to replace the O-ring just behind the water pump. Any ideas???
Also how hard is it to replace this part??

[boatmangc]

Sorry, doesn't sound right to me. The part you describe doesn't exist. There are 2 seals below the water pump base but you will need to pull the lower, drain the oil and then pressure test it.

[bobkyle2]

I would check the lower unit grease...It should be full and not watery...

Do you premix your gas.. Or does it have a auto mixer... If you premix your own gas.. It could just be excess oil..

[Underdog1]

I premix my gas and oil and last week I removed all fuel. Then replaced seal ring on botton end gear oil fill ports becoused I had noticed gear oil leaking from one. The seal ring was missing. I took the boat and ran it for about 30min. I no longer have the issue.

[bobkyle2]

Thats good to hear!!