1970's Mercury PTT Dual Piston wont bleed or move engine

[OilRig]

Hello All,
I am not as knowledgeable as I'd like to be with marine mechanics but I'll try my best to explain as best as possible my situation.

I have an early 70's (I think 1973) Mercury 1350 Thunderbolt outboard with a Dual Piston PTT with two hoses to each piston. The pistons have "45194" stamped into the side. I am not sure where I find the model of the pump I have, but it does state this on the side, " Reverse Lock Operation. To release, turn knob full right. To engage, turn knob full left, Use Only SAE 5W-30 service grade oil". Also the Electric motor on the pump is Arco-6217. The pump is located within the boat.

When I started, the whole system seemed to be fairly dry (I found the leak and already fixed it) and I am trying to bleed the pistons. I saw in other posts the pump is self bleeding, but the pistons are not. I see people use ATF for fluid but I have already proceeded with 5W-30. I am not sure which way that knob on the pump is suppose to be turned, but I assumed left? I have tried it both ways. Currently I can lift the motor up by hand when the pump knob is turned right, but it will fall down with the knob right or left. I have now disconnected the pistons from the motor to lay them horizontal. I have two flathead screws and two allen head screws on both pistons. From a previous post which I will add below I think the flathead screws are the bleeders? I don't know which hose is up or down, but both pistons have one large hose and one smaller hose. I have tried opening a bleeder and going a single direction to see if it will pump fluid or air out but I can't seem to get it to do either. If I manually press in and out the pistons, they will shoot out air and fluid from the bleeders. I think I just do not know how to properly bleed them. I'd like to understand how to bleed pistons, which hose does what. and what each screw port on the pistons are for. If anyone has any ideas, I'd very much appreciate it. I have gotten the pistons to take quite a bit of oil, but I am not seeing any results and before I rip this pump apart to check internals, I'd like to understand how it all works.

I followed this procedure below from another post on here on how to bleed and am wondering if this is correct or not.

The PTT pump is self bleeding. Fill the resevoir with 5W-30 motor oil (if existing oil is brown), or ATF (if existing oil is red). Pump will bleed itself when you bleed the rams.
Those trim rams have one grease fitting and two bleed screws each. Next to the grease fitting is a stainless steel slotted screw. Remove one of the screws, and run the PTT motor in the down direction. When only oil emerges (no air or air-oil mix), replace the screw and repeat with the other ram. Now remove the rams from the bracket and motor. Face the hydraulic line fittings up, and remove one of the other slotted bleed screws. The bleed screw is next ot the hydraulic fittings. Run the PTT motor in the up direction until all air or air-oil mix is out. Install screw and repeat with next ram. Refill PTT resevoir.

Main Question:
How to bleed pistons?
Which hose is up and which is down?
what all 4 screws are for on each piston?
What or where I can find the model of my PTT pump? This may help me find more info about these.


Thank you

 

[aburke120]

I have a 1975 merc 850 that probably has the same pump that you have. Mine has one solenoid that when raised will not lower the motor, I'm thinking that gravity lets the motor down to the run position. I had someone look at my hydraulic motor, and when I got it back, it raised the motor, and never has worked again. I unhooked my lines, and raised and lowered the 850 by hand dumping all the fluid into the bilge, then refilled it with 5w-30. There is a lever on the side of the motor that when used in the raised position will hold the motor in that position. Maybe together we can figure something out.

 

[Chris1956]

Oilrig: You posted the piston bleed instructions:

"PTT pump is self bleeding. Fill the resevoir with 5W-30 motor oil (if existing oil is brown), or ATF (if existing oil is red). Pump will bleed itself when you bleed the rams.
Those trim rams have one grease fitting and two bleed screws each. Next to the grease fitting is a stainless steel slotted screw. Remove one of the screws, and run the PTT motor in the down direction. When only oil emerges (no air or air-oil mix), replace the screw and repeat with the other ram. Now remove the rams from the bracket and motor. Face the hydraulic line fittings up, and remove one of the other slotted bleed screws. The bleed screw is next ot the hydraulic fittings. Run the PTT motor in the up direction until all air or air-oil mix is out. Install screw and repeat with next ram. Refill PTT resevoir."

What part is confusing you? The SS screw on top of the piston is down bleed. The one near the trim hoses on the piston is the up bleed.

Aburke: PTT system often have only one solenoid. That is used for the up direction. The down direction is wired directly theu the switch. The PTT pump motor should run in both directions.

 

[aburke120]

Chris1956 TY

 

[OilRig]

Chris1956,

Thank you for your response. I did follow that procedure but had no success, I thought I may be doing it wrong as it is vague on which screw is which. I will try one more time now that I know which screw is for up and which is down.

One question though, which way should that knob on the pump be turned?

Thank you,

 

[Chris1956]

Follow the instructions on the PTT pump. All the way CCW, yes?

Make sure to keep the PTT pump full as you bleed.

When you run the PTT pump, oil and air will shoot up out of the bleed ports. pulse it for a couple of seconds and watch for air bubbles with the pump off.

Remember to remove the trim cylinders from the bracket to bleed the up hydraulic circuit. The bleed ports must face up. I could usually put the top bolt on the trim bracket back in to hold the PTT cylinders facing up.