merc 850 lower unit leak

[hydrohumn]

My question is there's a hole on my lower unit just above the vent hole screw and now it's leaking gear lube. Is it a seal problem?

 

[MortenH]

Re: merc 850 lower unit leak

Welcome to iboats!

This sounds like the same experience I had this spring. I dont know exactly your model, but I dont think that there is supposed to be oil in that area. I believe that there is a seal thais failing, probably the one on the shift shaft or drive shaft. Try to drop the LU and do a pressure test.

-M-

 

[hydrohumn]

Re: merc 850 lower unit leak

thanks MortenH I will try that.

 

[hydrohumn]

Re: merc 850 lower unit leak

The manual I have shows how to remove the lower unit but doesn't show how to do a pressure check. There's not alot of troubleshooting in the manual I have. Is there a link or does anybody have info on how to do a pressure check on a 76 merc 850 thunderbolt ingnition series? any help would be greatly appreicated. Thanks

 

[MortenH]

Re: merc 850 lower unit leak

I just made a pressure tester from a bicycle handpump with a manometre and replaced the tyre valve with a plastic fitting from the hand pump used to pump gear oil into the LU. The clue is to use the fitting to get a tight connection, and use the hand pump and pump up about 15 PSI of pressure into the LU, and listen for leaks. Please let me know if I havent explained enough - if needed I can take a picture of the pump and post it.

-M-