What type of Hydraulic Pump do i get for 1980 Merc 90hp

[JMSports]

Just bought a 1978 Cee Bee Avenger with a 1980 Mercury 90hp Two Stroke I6 outboard on it. The engine runs and all the controls work, except there is no hydraulic pump in the boat. I have the old style pistons on either side of the engine, one has the grey and black lines on it and the other has no hoses.

My question is there are pumps on ebay and amazon for tilt trim that have 2 hydraulic fitting connections but I have 2 from each ram. The manual for the engine shows a pump that accepts 4 hydraulic hoses but I cannot find the correct one anywhere.

I need a correct inboard [remote] mount pump, the hydraulic lines, and if i can use the 2 hose pump, im gonna need either flare female tee fittings or a manifold to make the 2 lines from the pump connect to the four lines of the 2 pistons. Any help would be great.

 

[Chris1956]

You can probably get away with the two port pump unit. The dual cylinder ports for both up hydraulic circuits are connected together, as are the down circuits. You will likely need to rig up some sort of Tee connections, and remember that the hoses are different diameters.

The question I cannot answer, is whether the control valve in the new pump will work like the control valve in the original pump. I would think it will be close.

 

[JMSports]

Ive read that the pump that my engine is supposed to have is high pressure low flow prestolite style with only 1 solenoid.it also has a reverse lock on it. I cannot find any information on if I can install a newer and cheaper pump [250$] in place of this old style prestolite one [700$]

Anyone? Im so lost at what to do...

 

[Chris1956]

The OEM pump did have one solenoid for "UP", however, I do not think that is an issue. Merc used much heavier wiring on the down side eliminating the need for a solenoid. Later models had two solenoids. My guess is that the switch Merc wanted to use could conduct enough power for the "down" function, but not the "up" function, w/o a Solenoid.

Merc could have made the pump with one, two or no solenoids, and adjusted the wiring and switch to compensate, IMO.

As for the control valve. I would bet the pump you are considering does not have the manual release. If you have to tilt the motor by hand, you will need to loosen the up hydraulic hose and let the oil out. Not a big deal.

I would expect the control valve to work with the OB, as the function is the same for sterndrives, which is where you likely sourced this from..

 

[Alex from GA]

Look on ebay for an external 4 line outboard trim pump. I've seen several.

 

[JMSports]

Okay so i bought a pump on ebay that fits my style with 4 hydraulic hoses...but failed to realize that it was a 2wire and my harness on the control is for a 3 wire. Ive looked and looked with no definitive answer on if i can use this motor and how to go about wiring in solenoids so the trim switch works with this 2 wire pump. Does anyone know if this is doable?

 

[Chris1956]

I am surprised you found a 2 wire motor with a 4 hose PTT reservoir. I would not have thought those existed.

To be clear, the OEM motor has two wires plus a ground(3 wire motor). Power to the blue wire spins the motor in the up direction. Power to the green wire spins the motor in the down direction. The motor casing is always grounded.

A 2 wire motor needs 2 relays to operate. +12VDC is put on the blue wire by the energized relay, and the non-energized relay grounds the green wire to spin the motor in the up direction. The opposite is true for the down direction.

If you truly have a 2 wire motor, you will need to get 2 relays and do some simple wiring to make it work.

 

[JMSports]

I am surprised you found a 2 wire motor with a 4 hose PTT reservoir. I would not have thought those existed.

To be clear, the OEM motor has two wires plus a ground(3 wire motor). Power to the blue wire spins the motor in the up direction. Power to the green wire spins the motor in the down direction. The motor casing is always grounded.

A 2 wire motor needs 2 relays to operate. +12VDC is put on the blue wire by the energized relay, and the non-energized relay grounds the green wire to spin the motor in the up direction. The opposite is true for the down direction.

If you truly have a 2 wire motor, you will need to get 2 relays and do some simple wiring to make it work.

If i connect the power and ground from the motor to the battery then simply apply 12v to either blue or green, the motor spins in either direction without the use of relays.

 

[roscoe]

yes, but that pump is gonna draw some current.

You aren't gonna want to run that much through your tilt switch.

Use a relay set up.
Let the switch control the relays, and let the relays control the current.



Lots of used ones on ebay
"Mercury outboard tilt trim relay harness"

 

[Chris1956]

JMS, you have a three wire pump. one or two Solenoids were used with that pump, depending upon the year. On my '77 Merc, I had only an up solenoid. The Merc PTT control panel had switches heavy duty enough to eliminate the down solenoid,.