Trim up doesn’t work when on plane

[billodusa]

1996 Maxum 2300SR with 5.7 v8 mated to Alpha One Gen 2 outdrive. When boat is stationary or moving slowly, drive trims up and down normally. When boat is going fast enough to be on plane, trim up doesn’t appear to be working.
Has plenty of drive fluid but it appears milky.
Any thoughts on what to try first?

 

[Scott Danforth]

Most likely the cylinder seals need to be replaced

 

[tpenfield]

Probably leaking (somewhere), so the pump is not able to generate enough pressure to lift the drive except when there is minimal force on it ( stationary, going slowly).

Milky fluid is a clue. So, see where it is leaking . . . probably at the trim cylinder fittings or the ram seals.

 

[Lou C]

If you can get those end caps off changing the piston seals isn’t a bad job. Did that on my Cobra last year.

 

[Scott Danforth]

hydraulic cylinder seals last 15-20 years before they start leaking. your boat is 30 years old.

the piston seals are most likely bypassing, hence the reason it wont hold load.

the rod seal and wiper or the gland seal is most likely leaking, causing the milky fluid

 

[Lou C]

I guess I got lucky mine lasted 35 years!