Pitch/tilt not holding up

[tngoldwingpapa1]

I have a 2016 Mercury 90 hp attached to a Sylvan 20’ pontoon boat. Lately when I am finished boating I tilt the engine forward with the pitch switch and the engine drops back down in about an hour. Is there something I need to check/maintain?

 

[racerone]

Checked manual release valve?----Topped up the fluid ?

 

[tngoldwingpapa1]

Checked manual release valve?----Topped up the fluid ?

Checked manual release valve?----Topped up the fluid ?

Thanks. Guess this gives me something else to learn.