Pressure/Vacuum question

[jamowers]

I have a pre alpha MERC outdrive that leaks oil into water(outside boat). I pressure test the upper and lower seperately and they hold fine. I pull a vacuum on the lower and that seems fine. The upper half wont go any higher than 4-5 psi. Where do I start looking?

 

[jerryjerry05]

Re: Pressure/Vacuum question

Did you replace the seal between the cases?Small o-ring about the size of a big pen. Pressure should hold 11 -13# You say it only holds 4-5#
Put the cases together drain and put the pressure on and see where it leaks. Look around the prop shaft,the front yoke shaft,the shift shaft in the inside the housing. Come back and let us know.Jerry

 

[sarantis]

Re: Pressure/Vacuum question

and spraying some soap bubles on the above points may help you locate the leak easier

 

[jamowers]

Re: Pressure/Vacuum question

Pressure in the lower leaks when shaft turned found shift shaft bushing leak. Cant pull more than 3-4 vacuum in upper. Pressure holds 15 fine.

 

[Don S]

Re: Pressure/Vacuum question

I pull a vacuum on the lower and that seems fine. The upper half wont go any higher than 4-5 psi.

Assuming you are talking about pulling vaccum on the upper (in inches of vacuum, not PSI) that it will hold vacuum at 4 or 5 inches for a long time. If this is the case, tip the drive backwards so the ujoints are sticking straight up in the air, then put some heavy gear lube around the yoke. and try the vac. check.
The input shaft seal is a single lip seal not a double lip seal and will leak on vacuum easier than a double. Since there shouldn't be any water in the bellows, there is no use for the double seal.
If it holds with the heavy gear lube. It's ok.

 

[jamowers]

Re: Pressure/Vacuum question

I appreciate all the input, but I gave up and took it to the shop. I dont have the proper tools for the job. I will next year! I love tearing into new things. Learned alot doing what I did but the summer is passing me by and I gotta get on the water!!!!

 

[Dryon]

Re: Pressure/Vacuum question

Some may already know this, but for those that don't:
1 in. of mercury vaccum = 0.491 psi