150hp mercury xr4 trim lowers under load

[Phenix87]

I have an 89 mercury xr4 150hp outboard on a 18' bass boat. Fires right up no issues. I accelerate and my engine trims all the way down. I am not able to trim up while moving. The trim works great while not under load but no matter where I put it, it always goes right back to the lowest position. It gets up to just shy of planing out and you can watch it just lower right down.

Any help would be appreciated.

Thanks!

 

[Scott Danforth]

your trim needs servicing. you could have air in the sytem, or most likely you have dirt or other contamination in the system hanging up the valve. the thrust of the motor is exceeding the pressure holding capability of your trim currently. this would indicate some sort of contamination or damage to the trim.

 

[Phenix87]

Am I able to flush the system on my own? There are holes like the ones that used to be on my old manual trim motor on there as well.