Lower unit pressure test Tohatsu MFS 6B

~ 2010 Tohatsu MFS 6B

As I drained my gear oil I saw a thin line of milky color. Most of the oil was black. I've not noticed the milky line before when changing gear case oil though sometimes others do this service.

I thought I would try a pressure test to verify whether one of the seals has been compromised. Reading around I see tests of other units using a pressure test of 10 PSI. I've also seen others that start at 5 PSI then suggest checking up to 18 PSI. These have also had vacuum test numbers. I don't see anything specified in my four-stroke MFS 6B manual.

What would an appropriate pressure test be for this model? Is there an appropriate vacuum test too?

Thank you,
Harry

5 psi is plenty. Your LU pressure tester should be capable of both pressure and vacuum.
A little moisture could be from condensation. Myself, I would drain and flush thoroughly and then refill and check it again next normal oil change (50 hours).

pvanv said:

... Myself, I would drain and flush thoroughly and then refill and check it again next normal oil change (50 hours).

Click to expand...

Thanks for you quick reply.

"To flush", is this just a fill and immediate draining of the LU with gear oil?

Harry

Fill, run for a few minutes, drain and refill.