Trim Cylinder Moving Mysteriously.

[UncleWillie]

I took the out-drive off the boat a month ago for the winter.
The Battery was removed and the boat was covered for the duration.
A week ago I looked at it and one Trim cylinder had extended about 2 inches, all on it's own.




So I hooked the battery back up and hit the down button and heard the trim pump straining in bypass mode against the down stops.
The Port side Cylinder would not retract and was still extended. ???

So next I hit the up button and both Cylinders extended, in formation, Port side leading.
Once the Port Cylinder reached Max extension the Starboard side continued until it also reached Max extension and the trim pump went into bypass, again as expected.

Pressing the down trim caused both cylinders to retract equally to the fully retracted position which is what I wanted in the first place.

Now, it is cold and snowy and Ohio so there is not much boating going on, and the Cylinder has stayed in for the past week, so I really have no problem to solve.

So just out of boredom and curiosity;
Would anybody like to suggest a reason as to;

1. Why the cylinder extended in the first place.
and ...
2. Why the cylinder would not retract initially without being fully extended first?

(It is going to be a long Winter!)

 

[Don S]

Re: Trim Cylinder Moving Mysteriously.

Normal.
Temps heating the the cylinders will expand the oil and the cylinder that moves the easiest will usually move a little without being hooked to the drive (aka no load on them).
Not something to worry about.

 

[Frank Acampora]

Re: Trim Cylinder Moving Mysteriously.

The pistons inside the rams are sealed with O-rings. Sometimes an O-ring will jam in the cylinder. Since down will not have the same force on it as up (the override or bleed pressure is less because it is not needed), the ram will not retract. When you operate up, the jammed O-ring will free up and then when reversed the ram will retract normally.

This may or may not be a warning about O-ring failure. If in the future the trim bleeds down or refuses to function under load, you should check the internal O-rings.

 

[RRitt]

Re: Trim Cylinder Moving Mysteriously.

if i may interject a third possibility. when a system retracts, the piston shaft displaces air and the reservoir becomes pressurized. You have probably seen stickers on some engines saying not to remove filler cap unless engine is fully tilted up. Somewhere inside the pump is a pair of check valves that prevent the system from moving if the motor is not spinning. The spinning motor will create a pressure differential that pushes an actuator. Without the spinning motor then the actuator does not move and the system should not release or bleed pressure. However, the check valve is a very tiny seal that typically begins to deteriorate around 10 years regardless of how much or little you use the engine. High PSI, storing without engines blocks, cheap atf, water intrusion, or oil with detergents can all shorten the lifespan. The old Chryslers used a brass on steel valve and it would go 30 years or more. Most other brands are lucky to make it past 18.

At any rate, the piston extension is probably just the internal reservoir pressure slowly bleeding past the check valve. Don't even give it a second thought. When the engines starts bleeding down or the top seals show cracking then fix it. Until then, happy boating.

 

[cyclops2]

Re: Trim Cylinder Moving Mysteriously.

another

air trapped during normal operation can collect in a cylinder & the hose farthest from the resivoir. Then heating of the air moves it more than the the one with less air in the lines & cylinder.

No drips or cracking noises of a binding cylinder ? Run it.

Do check the oil level with the cylinders FULLY RETRACTED. Add any needed while retracted.

 

[theBrownskull]

Re: Trim Cylinder Moving Mysteriously.

Normal unless there are leaks somewhere.

 

[smoedog]

Re: Trim Cylinder Moving Mysteriously.

go google "Charles Law"

Don't know how many times I have to explain to a crew chief why their reservoir overflowed when a plane lands after they serviced it to much

 

[Friscoboater]

Re: Trim Cylinder Moving Mysteriously.

Don is 100% right