trim problem on c85 tlrq

[cyrillefrenchy]

first thank's to all of you, i learn a lot on this forum
my problem isn my c85 tlrq on a cobia 17' center console, the trim tilt works fine going up or down and can stay up for days but when i ride the boat(start with the trim all the way down)and i trim up a little bit to get the bow up, the engine goes back all the way down by itself, i have to trim up again for maybe 10 12 times to be able to see the trim staying at the right position, and after it works all day.
the oil level is right, the oil is clean, i tried to open and close the release valve on the side,(the one used to trim up and down if the electric part does not work) , still the same...
seems like a little valve or something is stuck when cold
i think it's internal, right? any idea?
thank's
excuse my french-english
frenchy

[slim]

yes it sounds like you have a bad relief valve. it is located in the front of the trim unit so you have to take the motor off the boat to get to it.

[cyrillefrenchy]

hello slim
ok , what is this valve, and what is it for?
i plane to take the engine off , i have an exhaust leak between the powerhead and the mid section, so maybe everything will be done at the same time
any advise will be apreciated
frenchy