125 Mercury Trim and Tilt Problem

[HennieR]

I recently acquired 2006 Mercury 125 and has been used 78hrs on a Sensation boat, this is a awesome combination and give us lots of enjoyment. However I seem to have a problem with my trim and tilt system. It will not keep its position (runs down on its own) it seems to have an internal bypass or leak. As the boat mechanics in South Africa is not of the highest quality and is more interested in money than assisting a customer is it possible for a trouble shooting answer. I am a qualified aircraft mechanic and therefore am reasonably capable to repair this problem if directed probably.

[boats.net]

Sounds like a leak in the trim/tilt valve body.