Prestolite single solenoid trim pump

[K&C Speed]

Good Day
I'm looking for help on my old Prestolite trim pump 1977120 Mercruiser MC-1. I had everything off and apart to rebuild my transom. I reassembled the trim assembly, wiring and hydraulic lines what I believe to be correct.
The leg trimmed down ok. but not up.. Won't go up in neutral.. Actually, I cant even get a click from the trim solenoid. I put my control in reverse.. I can get the pump to activate in the up position (laboring I might add) with hydraulic fluid shooting out the bottom of the pump reservoir.. I think its the the return line where its coming from.. but not really to sure. This Trim pump was working prior to me removing it last fall. One button down and two buttons up and out. the single button up for trim was not functional. The power fuse and circuit breaker were absent.
So, I'm new to boats but willing to learn.
Any suggestions would be greatly appreciated as I have come to a place I'm not really sure what to do from this point forward.
Thank You

 

[alldodge]

Sounds like down (green) is using the solenoid when it should be the up (Blue). Down requires less power so it comes direct from the switches. The solenoid is used for up when current is higher

 

[K&C Speed]

Thank you for the wiring schematic. It appears as though I have wired it correct. In the photo I have ran a Jumper wire to bypass the limit switch. I’m starting to think the solenoid has gone bad. I also found a crack in the plastic terminal block that the wiring from the power trim motor wiring goes to. Perhaps power is cross feeding from the blue wire to the green wire?
As far as having to put the Shifter in reverse.. Is it possible the reverse lock out is not working correctly or requires adjustment? I changed out the micro switch for a new one as the old one was cracked upon removal. I also changed out the Mercontrol Shifter for one that fits flush on the panel.Instead of the black box external style Mercontrol . not sure if that has any bearing on the issue with having to put the shifter in reverse to energize the up out switches.. again, thank you for your response .. any help is appreciated.
Thanks

 

[alldodge]

The shifter would have no issue with yours. Least those solenoids are cheap enough

 

[K&C Speed]

Ok on the Shifter.. Think I'm going to pull the trigger on a new solenoid. Thanks

 

[K&C Speed]

I was able to adjust the reverse lock out so the Trim up/out can now be operated while in neutral. The micro switch is now closed in neutral completing the circuit. I was able to trim up a little but hydraulic fluid was pouring out of the bottom of the trim motor valve body. I have an O ring kit on order and a new marine grade solenoid coming as well. The old solenoid is likely ok but it being 45 years old I have elected to change it out anyway. Think this problem might be busted.. See what transpires after the O ring kit is installed. Thanks for the input.

 

[K&C Speed]

Thank you for the wiring schematic. It appears as though I have wired it correct. In the photo I have ran a Jumper wire to bypass the limit switch. I’m starting to think the solenoid has gone bad. I also found a crack in the plastic terminal block that the wiring from the power trim motor wiring goes to. Perhaps power is cross feeding from the blue wire to the green wire?
As far as having to put the Shifter in reverse.. Is it possible the reverse lock out is not working correctly or requires adjustment? I changed out the micro switch for a new one as the old one was cracked upon removal. I also changed out the Mercontrol Shifter for one that fits flush on the panel.Instead of the black box external style Mercontrol . not sure if that has any bearing on the issue with having to put the shifter in reverse to energize the up out switches.. again, thank you for your response .. any help is appreciated.
Thanks

So… I was able to get the leg to go up and down in neutral and reverse.
I wasn’t able to get the leg to trim up while in forward. I can’t figure out how to engage the micro switch on the reverse lockout so I can trim up.. there is not enough adjustment on the reverse lock out arm without adjusting the shift cables out of adjustment.. .
Someone out there must have experience on these old pre alpha drives.
Please .. any suggestions or advice would be appreciated
Thanks

 

[K&C Speed]

Here’s a pic of the lock valve and micro switch

 

[alldodge]

Hey @Bondo need some help

 

[Bondo]

Hey @Bondo need some help

Ayuh,..... Sorry, but my answer to fixin' those old trim systems is to rip it all out, droppin' in the new style plastic tank pump, 'n go boatin',.....

 

[K&C Speed]

Ok.. changing the trim system with the newer style plastic tank eliminates the reverse lock valve problem.. I assume you just plug the fluid lines that run into it. Do you also have to change out the rams to the newer alpha 1 type? What trim senders can be used? Would need to know what all what I need to do to change over the system.

 

[alldodge]

Yes, just reroute the lines. All work is inside so your trim will work as before
Here is a thread where guy asked same

https://forums.iboats.com/threads/trim-pump-upgrade-for-older-mercruiser.648369/

 

[K&C Speed]

Yes, just reroute the lines. All work is inside so your trim will work as before
Here is a thread where guy asked same

https://forums.iboats.com/threads/trim-pump-upgrade-for-older-mercruiser.648369/

Ok Thank you.. I’ll follow up on that.. sure would be nice to finish upon this.. want to get this thing on muffs to see if she’ll run