Need Help Trim/Tilt problem

[luv2flycessna]

1984 150HP Mercury Blackmax

Having a problem with my Trim/Tilt motor and/or pump.
The engine goes up just fine sitting still or on the lift. After the motor is up and I try to go down it starts off great the slowly slows down and struggles.  Underway it will go up to about to about where the cavitation plate is level but no higher.
I would think it should go down easier than up, while under way it is hard to get it to go down. Hopefully I have explained this enough, if not let me know what else you may need to know.
 
Any Ideas?

Here are some pics of the Trim/Tilt motor and pump.

[Marcq]

I'm not familiar with that kind of a setup but have you check the hydraulic fluid level ?
Marc..

[luv2flycessna]

I'm not familiar with that kind of a setup but have you check the hydraulic fluid level ?
Marc..

Yeah even changed it thinking it may be old or have water or something in it and was all ok when I Changed it,  a little sludgy(msp) but even with new oil still doing the same thing.

[Hawg Hunter]

Have you changed the relay switcch ?

[luv2flycessna]

Have you changed the relay switcch ?

Relay Switch? Where would this be at? Are you talking about the switch on the throttle control?

Would a switch cause it to Work sluggish down and not up?

I have been working it right at the solenoid by shorting across the terminals while it is on the lift and does the same with the controls on the throttle control or at the solenoid itself.

[Capt. Bob]

Could there be air in the system?
I'm not a Merc guy but I think there is a check valve in their system that may be bad thus causing the slow return you are experiencing. http://en.allexperts.com/q/Boat-Repair-2123/mercury-tilt-trim-motor.htm
Your motor seems to be working fine so I'd look to the pump and maybe the check valve.

Good luck.

[luv2flycessna]

Could there be air in the system?
I'm not a Merc guy but I think there is a check valve in their system that may be bad thus causing the slow return you are experiencing. http://en.allexperts.com/q/Boat-Repair-2123/mercury-tilt-trim-motor.htm
Your motor seems to be working fine so I'd look to the pump and maybe the check valve.

Good luck.

Sounds like it could be the check valve, Will have to read up on it and see what I can do, Would make sense. Seems to be fine at first then slowing down as it comes down, So it is ok unitil pressure builds in the hose.

[John Jones]

You may have hydraulic or electrical issues but be sure the tilt tube is not rusted up inside.  A friend bought a boat with twin Yamahas and one of the motors would not go down.  It ended up being nothing wrong with the tilt/trim system.  The tilt tube was so corroded the motor would not even free fall with the bypass open and a 200lb guy swinging on it.  It took days of forcing in grease and working the motor up and down to finally get the motor to go down easily.

[GoneFission]

I'm pretty sure you have what is known as a Mercury "C" trim/tilt.  I has one cylinder, not 2 or 3 like the "A" and "B" systems.  Have you bled the air from the system?  You have to go through several cycles up and down to get the "C" tilt system fully filled:  

1.  Manual release valve in - turned full right - and fill/vent screw out 1 1/2 turns.
2.  Use trailer switch to raise motor to full up.
3.  Fill pump to "add" line on dipstick if needed to go full up.
4.  Use down switch and take to full down.  If pump sounds like it's running without oil or if the outboard does not go all the way down, fill to the "add" line on the dipstick.  
5.  Go full up and full down 3-4 times - each time, fill to the "full" line on the dipstick when the motor is in the full up position.   Keep going up and down until the level remains full and no more filling is needed.
6.  Tighten the fill/vent screw and cycle up and down.  Open the fill/vent screw 1 1/2 turns at the bottom to do a final vent on the reservoir.  Close the fill/vent screw and you should be good to go.

Hope this helps - see ya on the water!