Why does trim work at dock, but not while running?

[Fast Shafts]

Mercury 250 XS, the engine trim works at the dock but not while under load (onplane). Any idea why? Thanks!

[WaterZebra]

Mercury 250 XS, the engine trim works at the dock but not while under load (onplane). Any idea why? Thanks!

Where is your ignition key position when you are at the dock?

[David - WI]

If you trim up a little bit and then take off... does it stay trimmed up or slam down?

It sounds like either a pressure-relief is stuck or a manual bypass valve is open a bit??

[WaterZebra]

If you trim up a little bit and then take off... does it stay trimmed up or slam down?

It sounds like either a pressure-relief is stuck or a manual bypass valve is open a bit??

Good point! Is the problem caused by electrical or hydraulic issues? Did you check your trim pump reservoir oil level?

[Jim Speros]

Another possibility if you have remote trim pump. The pump may be hook up backwards. Up is really down on the hydraulic side. When you activate the blue wire it should be going up. The down side does not create as much pressure.

[Fast Shafts]

Thanks for the responces.
The engine is running at the dock when the trim works
There is oil in the resevoir.
The engine does stay up when trimmed up at dock.
I'll have to get someone to check the pressure relief valve-I dont know what this is, or how to do it.
Thanks Again!

[25two.stroke]

Thanks for the responces.
The engine is running at the dock when the trim works
There is oil in the resevoir.
The engine does stay up when trimmed up at dock.
I'll have to get someone to check the pressure relief valve-I dont know what this is, or how to do it.
Thanks Again!

Make sure the manual bypass (plastic big straight head screw on the on starboard side of the transom clamp) is tight. It doesnt need to be super tight, just snug by hand. If that is loose the pump will run and not lift the motor or lift the motor and not hold it there under a load.

If you trim up a bit and then run does it fall down or stay where you trimmed it to?

[OnPad]

Something to think about. A electric motor draws more amps when loaded. With that in mind your motor could be stalling due to bad brushes, com, or you could have a bad relay.

[Fishwhisper]

Is the trim on a throttle that is in a different position when on plane? If so could be electrical connection problem in the switch/throttle.