Mercruiser Pre-Alpha Trim Troubleshooting

[CableGuy1978]

Hello,

Tried searching the threads for an answer but unable to find exactly what I am looking for...

Having some problems with my power trim. The outdrive is currently off the boat as I have replaced the engine coupler, and awaiting alignment. I have had problems with the tilt not working so well on the Up, but worked find on the Down. I took apart the switch on the shift lever and tried touching the wires directly, which did activate the pump. However on Up, the pump seems to be working hard as it runs a lot faster on Down. There is no load on the pistons either, and there is no movement from them on either direction when the pump is on. I am trying to troubleshoot the cause. I am also having difficulty identifying the type of pump it has as the ones in the manuals don't look the same.

Is the reservoir supposed to completely filled, as mine appears to be between 1/2 and 3/4 full.

Also I hear tell that these systems are supposed to be self bleeding as air in the system was a concern as well.

How likely is it that both pistons have seized. The boat has sat for 2 years steady in storage outside.

I had it to a marine shop awhile back for the same problems and after they charged me for some sort of repair job, I never got to try it out as I had a bad coupler and no money to fix it at the time. So I am going at it myself, and looking for some direction.

Thank you for taking the time to read this far, and for any info!

 

[swihartart]

Re: Mercruiser Pre-Alpha Trim Troubleshooting

A few things to try.

disconnect the lines from the cylinders, run the pump, do you get fluid squirting out? (you may want to place them in some kind of container in case it does). If so, pump works but cylinders have issues.

Is the reservoir supposed to completely filled, as mine appears to be between 1/2 and 3/4 full.

If your reservoir is square and metal you have a prestolite pump.

Yes, full with vent screw (the one on top) cracked to vent air. The fill screw sits just below the vent and is "notched out" of the reservoir housing. They are self-bleeding for the most part but if you change cylinders or empty the system, it helps to crack the lines at the cylinders and run the air out as much as possible then retighten and run drive up and down to get the rest out.

 

[CableGuy1978]

Re: Mercruiser Pre-Alpha Trim Troubleshooting

Ya it is square, and is shown multiple times in the Seloc manual. I filled the reservoir as it was down quite a bit. After reading through the manual several times, I traced the all of the wiring and identified it according to the drawings, everything lines up properly. The motor works as normal when pressing the Down button. It does nothing when pressing the Up button. The manual suggests connecting the blue wire from the harness plug directly to the positive side of the battery bypassing all switches etc, nothing happens still, though there is definitely voltage present as sparks are visible when touching the wire to the terminal.

I bypassed the reverse lockout switch as well in case it was faulty.

What doesn't make any sense to me is how the pump will work in one direction and not the other. Could it be the solenoid? I still can't seem to figure out if it is electrical or hydraulic problem. I'm at the point where I am going to look for a replacement pump.

Thank you very much for the reply. I very much appreciate any and all ideas.

 

[Doernuth]

Re: Mercruiser Pre-Alpha Trim Troubleshooting

Does your system have one or two solenoids? If two one could be bad. Switch the wires from one to the other and see if it now goes up but not down. If so you have a bad solenoid.

If system only has one disregard the above....

 

[CableGuy1978]

Re: Mercruiser Pre-Alpha Trim Troubleshooting

Ya this one only has 1 solenoid. But I know what you mean as I have seen some diagrams of pumps with 2 solenoids.

Thank you very much for the post anyway.