[smokewagon]

I have a 1999 Yamaha 100hp 4 stroke, after changing the water pump with a new kit I keep getting milky oil out of the gearcase, I have changed the oil 3 times, I installed new seals on both the top shaft and prop shaft. I did the pressure test at 11 psi for 24 hrs and it held steady. What have I done wrong? Why the milky oil? Where is the leak?



stumped,

Smokewagon,

[Mas]

Now do a vacuum test! Both pressure & vacuum tests must be done to ensure a properly sealed case. A slight vacuum is created when the case "cools" down and draws water in. Although the case does not get hot, it does increase in temp slightly during use, when it cools a vacuum is created and could draw water in.

MAS

[smokewagon]

OK, I try the vacuum test also.


smokewagon,

[smokewagon]

OK, I did the vacuum test and it held steady, also I changed the oil and did a water test run for 1 hour, drained the oil and it was milky, so I pulled the lower unit off to do a good look over, I pulled the water pump apart and the 2 seals on the drive shaft were all milky as was the impeller, so I replaced the water pump again, I also did the driveshaft seals, Which way do the seals go in?? The manual shows the lip facing up, Is this right??


smokewagon,

[rodbolt]

both lips face out on both the prop shaft and drive shaft.
remember a trace amount of milk in the case will make the next change look milky.

[smokewagon]

OK, seals are in correct, I'll put some time on it and check the oil again.

thanks, Rodbolt


smokewagon,

[lundfrie]

Hey!
Any luck with your leakage?

Have the exact same problem with my F50 1999, and the mechanics are out of ideas what to do.