My 2004 Bravo X1 Drive when trimming up or down shudders, has slip stick type of movement. It did not used to do this. It has about 380 hours on it. The fluid reservoir is full and the drive shaft spline is fully lubbed. The merc tech line says to do a pressure test on the pump system.

I am interested in hearing if anyone has experienced this symptom and what was the cause/fix.

I'd guess one of the rams has a bad seal.

If I disconnect the trim cylinders from the lower unit and operate the trim switch the bad cylinder should act up?

The electrical connections were all good. I disconnected the cylinders from the drive so no load. The pump would randomly labor at different levels of strain as the cylinders were trimmed out or in. The cylinders took turns sticking, shuddering or conversly running smoothly. Sometimes the cylinders would just stop and the pump would stall completely. Sometimes if I would release the trim button and immediately reapply everything started again to work correct....only briefly.

Thanks for the thoughtfull brainstorming and suggestions.

Yesterday's testing with both cylinders disconnected from the drive and therefore operating at no load with the drive (and sensors) at the full down position and now static would seem to take the electrics mostly out of it. Also the pump would still randomly labor at different levels indicating load/strain on the fluid pump as the cylinders were trimmed out or in. The cylinders took turns sticking, shuddering or conversly running smoothly. Sometimes both cylinders would just stop as the pump would stall completely. Sometimes on these occasions if I would release the trim button and immediately reapply everything started again to work correct....only briefly. The sounds the trim motor made during this testing versus the movement, or lack there of, was like the fluid resistance was overloading the pump motor as apposed to intermitant electrical connection problems.

I would like to hear about the potential hydraulic reasons and or fixes for my trim issue that you may be aware of. I have so far heard that dirty fluid could be the cause and a simple fluid change may fix the problem. Also suggested was that the trim cylinder piston seal (seals?) seperating the up pressure side from the down pressure side of the cylinder could be bad/leaking. Corrosion build up between the of the aluminum trim cylinder body and stainless steel ram shaft (I checked mine and clear). Your thoughts experience versus these or other causes?

check the pump solenoids, i have had issues with them,
Is the drive spongy? ( can you move it up and down when the trim cylinders are connected)? the pump could screwed. disconnect the lines at the pump and test operating pump pressure

Can the pump pressure test be done on the pump outside of the boat like if I take it to a dealer and aske them to test it? I do not have the test gage and manifold test equipment.