V-P I/O Trim Hydraulic Doesn't Hold

[cxcamp]

I have a '95 Wellcraft with a V-P SX outdrive and 4.3 GL motor. The power trim will no longer hold the motor in the up position, it slowly sags back down (I have to use trailer clips to tow it). Any suggestions on what needs to be repaired? I assume a seal has gone.

thanks for your help,

cxcamp