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290 trim issues

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Rscottdds

Regular Contributor
My outdrive will slowly drop to full down while underway. I usually run at a -2 or 3 but lately after being up on plane for 5 minutes or so it will be all the way down to full down (-6 maybe?) What's the usual cause and fix for a hydraulic trim that slowly drops?
-Robert
 
Regarding the cylinder itself, the base end hydraulic fluid volume is larger than that of the stem end hydraulic fluid volume (the stem itself consumes volume).
If the pump valves are holding, it's pretty tuff for the base end hydraulic fluid volume to find a place to go.
In other words, it is more likely that your pump valves are not holding.



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RicardoMarine said:
Regarding the cylinder itself, the base end hydraulic fluid volume is larger than that of the stem end hydraulic fluid volume (the stem itself consumes volume).
If the pump valves are holding, it's pretty tuff for the base end hydraulic fluid volume to find a place to go.
In other words, it is more likely that your pump valves are not holding.



.
Click to expand...

Thanks. How difficult is it to replace the valves?
Thanks,
Robert
 
Rscottdds said:
Thanks. How difficult is it to replace the valves?
Thanks,
Robert
Click to expand...

Robert, if a valve or valve seat has debris in it, it will prevent the valve from seating properly, preventing the cylinders from holding trim.
In many cases the pump valves can be accessed and can be cleaned.


A correction to my previous post.


Regarding the cylinder itself, the base end hydraulic fluid volume is larger than that of the stem end hydraulic fluid volume (the stem itself consumes volume).
If the pump valves are holding, it's pretty tuff for the base end hydraulic fluid volume to find it's way through a leaking cylinder piston seal and find a place to go.
In other words, it is more likely that your pump valves are not holding.




.
 
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