Heres the symptom. Haven't had the Sonic on the water yet-ICE. When I trim the drives up sitting on the trailer, the starboard pump sounds like it cavitates and trim movement slows on that drive. Both reservoirs have the proper level of what looks to be Merc trim fluid or 30 weight engine oil. How to diagnose further? KS

the valving in the pump is usually the problem.you can buy new pumps cheaper than bying the parts to repair the pump in question.

Sometimes the pickup tube will get clogged.

A pickup tube in the reservoir?

i never heard of that before.what can get in the res except for fluid?

Wonder if it is a voltage problem on the weaker pump? How are the pumps wired?

Ok, maybe a better description would be, the electric motor sounds fine, the hydraulic area sounds normal until about 1/3 trimmed out, then it sounds like air cavitation? Do these have to be manually bled somehow? Yes, there is plenty of normal color and texture oil in the reservoir. Thanks for the input, KS.

I can't remember 8 or 9 years ago, I removed the top pump and their was a screen in there that had some crap in the screen.

remove the cap and look inside the resivour,,if its a plastic tank the red fluid dye's the plastic and can fool you by making you think theirs fluid in it,,

Update. Although the fluid looked ok, I used my vacuum oil change pump and replaced the trim pump oil in two steps, now all seems normal. According to Merc these are self bleeding upon running in and out. Will let you know if it is a long term solution. Really didn't think changing the fluid would make that much difference.