85hp PTT help

Hi all,
Have a 76 - 85hp merc with PTT. Pump is the A series, 4 hose , 2 cyl. Noticed when I applied additional throttle in reverse the engine would jump a bit, Does this everytime. Didn?t before.
Checked out all mounting hardware, and nothing is loose . I?m quite sure the problem is my
pump. My merc manual states a defective check valve, will cause trim cylinders to fail to hold
reverse thrust. (By the way, oil level is OK.)
I am guessing this check valve is in the control valve assy. As I cannot find an exploded view
anywhere. Manual also states control valve is not repairable and must be replaced as an assy.
I was going to pull the control valve, Inspect and clean shuttle plate and replace the 4 O-rings.
Can I get into that control valve to see if there is a problem with a check valve. I?m sure
someone out there has opened one of these up. Appreciate any guidance.

Thanks in advance
hereto

Re: 85hp PTT help

Hereto, make sure the manual reverse lock is locked. It is the black knurled know that screws into the control valve under the pump body. The control valve contains the check valves. Remember, the pump simply runs both ways. The "down" check valve must be calibrated to hold reverse thrust, but still allow the motor to tilt up. Ditto on the "up" check valve. It must hold full power forward thrust, yet still allow the motor to trim/tilt down.

As far as I know those control valves are not repairable or rebuildable, as you were also told. Someone on this forum hinted that they had success fixing one.....

if there are no oil leaks, then the control valve O rings are fine. Maybe you can change the oil. Any chance someone put bad oil in the unit?

Re: 85hp PTT help

Thanks for the response Chris1956. I have no oil leaks so I guess my o-rings are ok. The oil in the pump is black, and no one has messed with this pump. I have no idea how long this oil has been in it. The pump has been working great the last 5 yrs. since I have owned it.
I will change out the oil and would greatly appreciate any guidance, will I have to pull the pump or could I pump it out the fill hole? Any pointers as to flushing the system would be greatly appreciated. And yes the manual lock is closed.

Thanks
hereto

Re: 85hp PTT help

Hereto, Dump the oil out of the pump. Fill with fresh 5W-30 motor oil. Crack the PTT hoses at the control valve and run the pump down and up as necessary to bleed out all the old oil. Refill the pump. Now open the down bleed screw on one PTT cylinder. It is a flat head SS screw, next to the grease fitting on the top of the cylinder. Run the pump down until you see clean oil. Replace the bleed screw Repeat with the other cylinder.

Now top off the pump, and remove both trim cylinders from their mounting. Reverse them and replace the upper trim cylinder mounting bolts. The place where the trim hoses connect should be now facing up. Remove the up bleed screw (next to the hose connections) and run the pump up until you seen clean oil. Reinstall the bleed screw and repeat with the other PTT cylinder.

Restore the PTT system to operating configuration, and retest operation.

Re: 85hp PTT help

Hereto, I have taken them apart and believe me you don't want to. On the bottom I hope you know that release valve works in the opposite direction (clockwise is open). Buz