2003 Mercury 90-HP Power Trim: Diagnosis and Repair

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  2003 Mercury 90-HP Power Trim: Diagnosis and Repair

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Author Topic:   2003 Mercury 90-HP Power Trim: Diagnosis and Repair

dipilato posted 02-11-2009 01:47 PM ET (US)
Woke up this morning to find my engine lowered into the water. Sure that I had trimmed it up last time I used it. Went to trim it back up. Nothing. Heard the typical trim sound but it sounded a bit different than normal. No movement of the engine in either direction.
Was able to loosen the relief screw and use the manual up and down and get the boat on the trailer with the engine up on the support bracket. (That thing is heavy.) Would like to troubleshoot and see if I can diagnose. Done some digging on the site and can't seem to find much relevant info. Nothing in the manuals that I have.
Anyone had this problem, or have any info or old threads that could help?
Thanks!
Tohsgib posted 02-11-2009 02:42 PM ET (US)
Probably low on fluid. Fill it, cycle it and keep filling after every cycle and find out where it is leaking from. It is just ATF fluid.
dipilato posted 02-11-2009 04:03 PM ET (US)
Assuming just to do that just remove the white plastic hex nut and fill? On cycling, do you mean just through running the trim button up/down?
jimh posted 02-12-2009 12:48 AM ET (US)
Power trim systems contain two distinct segments: the electrical portion and the hydraulic portion.
The electrical portion has straightforward and simple circuitry. With a basic understanding of electricity and minimal test equipment you can assess the electrical operation. Switches control relays that run a motor or two.
The hydraulic system is substantially more complex. Other than checking the fluid level and making a careful visual inspection for leaks, there is not much that can be done simply. If the engine drifts down from the tilted-up position, you likely have a check valve which is not operating properly. These valves are typically contained in an internal assembly, and you generally cannot easily repair or replace them without tearing down the assembly.
If fluid has escaped from the system and been replaced with air, you will see erratic operation. Often re-filling the system to the proper fluid level, then operating the ram through its entire range a number of time with the filler cap removed will permit the system to bleed air from the lines.
Your owner's manual should give you advice on any procedures to use when refilling the hydraulic system with fluid. Be sure to use the proper fluid as recommended by the engine manufacturer.
If you decide to dig deeper into the hydraulic system, you will probably need to buy the factory repair manual for guidance.

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Author	Topic: 2003 Mercury 90-HP Power Trim: Diagnosis and Repair
dipilato	posted 02-11-2009 01:47 PM ET (US) Woke up this morning to find my engine lowered into the water. Sure that I had trimmed it up last time I used it. Went to trim it back up. Nothing. Heard the typical trim sound but it sounded a bit different than normal. No movement of the engine in either direction. Was able to loosen the relief screw and use the manual up and down and get the boat on the trailer with the engine up on the support bracket. (That thing is heavy.) Would like to troubleshoot and see if I can diagnose. Done some digging on the site and can't seem to find much relevant info. Nothing in the manuals that I have. Anyone had this problem, or have any info or old threads that could help? Thanks!
Tohsgib	posted 02-11-2009 02:42 PM ET (US) Probably low on fluid. Fill it, cycle it and keep filling after every cycle and find out where it is leaking from. It is just ATF fluid.
dipilato	posted 02-11-2009 04:03 PM ET (US) Assuming just to do that just remove the white plastic hex nut and fill? On cycling, do you mean just through running the trim button up/down?
jimh	posted 02-12-2009 12:48 AM ET (US) Power trim systems contain two distinct segments: the electrical portion and the hydraulic portion. The electrical portion has straightforward and simple circuitry. With a basic understanding of electricity and minimal test equipment you can assess the electrical operation. Switches control relays that run a motor or two. The hydraulic system is substantially more complex. Other than checking the fluid level and making a careful visual inspection for leaks, there is not much that can be done simply. If the engine drifts down from the tilted-up position, you likely have a check valve which is not operating properly. These valves are typically contained in an internal assembly, and you generally cannot easily repair or replace them without tearing down the assembly. If fluid has escaped from the system and been replaced with air, you will see erratic operation. Often re-filling the system to the proper fluid level, then operating the ram through its entire range a number of time with the filler cap removed will permit the system to bleed air from the lines. Your owner's manual should give you advice on any procedures to use when refilling the hydraulic system with fluid. Be sure to use the proper fluid as recommended by the engine manufacturer. If you decide to dig deeper into the hydraulic system, you will probably need to buy the factory repair manual for guidance.