1975 85 hp tillt and trim cylinder rebuild

[beanutputter]

I bought a tilt and trim unit off eBay for my 1975 85 hp Johnson. Did the install and one of the hydraulic cylinders is not working. Anybody have any ideas to check out? Are the Cylinders hard to repair? And the big question, what parts do I need to rebuild it.

 

[ezeke]

Re: 1975 85 hp tillt and trim cylinder rebuild

The unit has two cylinders, one is TILT, the other is TRIM; the one closest to the pump motor is the tilt.

The trim and tilt cylinders will only operate together for the first 15 degrees of travel from the down or running position. This TRIM function is to overcome the force of the water when the TRIM function is in use on the running boat.

Afterwards, the rest of the tilt travel is completed using only the tilt cylinder.

 

[beanutputter]

Re: 1975 85 hp tillt and trim cylinder rebuild

It is the trim only cylinder but it is not moving at all. When I try to lower the motor to the trim range, the trim only cylinder will not retract and the motor starts trying to twist in the bracket.

 

[beanutputter]

Re: 1975 85 hp tillt and trim cylinder rebuild

well I said it would not move at all, but it did extend then would not retract. If I tried to retract it out of the bracket what would happen to the trim only cylinder when the other reached the trim position.

 

[ezeke]

Re: 1975 85 hp tillt and trim cylinder rebuild

Edit: From the totally down position, both move together under power for 15 or less degrees, then only the tilt cylinder should move under power.

The trim cylinder will stay extended until both cylinders are completely withdrawn again.

Once all hydraulic power is directed to tilt only, there will be a noticeably faster speed to the extension of the tilt ram.

 

[HighTrim]

Re: 1975 85 hp tillt and trim cylinder rebuild

The valves on these can be a real bugger to diagnose or repair, especially without the manual and the proper equipment. That is likely your issue.Do you have the factory manual?

I would try first though letting it down manually, via the manual release screw, drain the fluid, then re top up and cycle.

 

[ezeke]

Re: 1975 85 hp tillt and trim cylinder rebuild

I don't think its mounted yet, hence some confusion.

The seller said that he guaranteed the unit so I think that it may be OK.

Definitely get the service manual for your motor; Section 9 is completely devoted to the Power Tilt and Trim.

http://cgi.ebay.com/ebaymotors/John...10103828551QQptZMotorsQ5fManualsQ5fLiterature

 

[beanutputter]

Re: 1975 85 hp tillt and trim cylinder rebuild

THANKS A LOT to both of you for your help and time.

I have the manual and the system has been mounted, unmounted, and now remounted.

During the unmount, I removed all lines and cleared completely all fluid and contaminants. Fluid was very milky. Then I managed to manually move a very stubborn trim only cylinder. After depressing both cylinders removing as much fluid as I could, I reassembled the whole thing, and then remounted it to the motor. I followed the manuals filling directions and all seemed to be going well. It raised fully with no problem, however when lowered, all goes well until it gets to the trim position, then you can see the cylinders load up like a wood splitter. It will pull itself all the way down but under a fair load. The motor even shuts off from the thermal cutoff. It is a lot better than it was but a long ways from right.

 

[ezeke]

Re: 1975 85 hp tillt and trim cylinder rebuild

Did you remove the original shock-absorber-like cylinders (2) from the midsection? The original manual tilt assembly shocks weren assist cylinders.

When lowering the motor your newly added tilt and trim cannot overcome them without undue strain and risk to the PT&T.

Removal of those shocks is required. While not absolutely necessary, they should be replaced with the shock absorbers # 385532 if you can find them.

 

[beanutputter]

Re: 1975 85 hp tillt and trim cylinder rebuild

OK, I took the unit back off and ran it on the ground from the fully compressed position. The starboard cylinder works well with no problems. The port cylinder would not move at all. I cracked the line and ran the pump to make sure the line was not blocked, seemed ok. I went ahead and manually operated the port cylinder to about 3 in up. With all lines tight i ran the system to full up, starboard worked fine, no movement on port as expected. I then ran system to full compress. When the starboard cylinder got to the trim range the port started to erratically POP out (the wrong direction), but only moved maybe 1.5".
Now I an really lost. I don't really feel confident it is the cylinder, starting to think maybe a valve. Any ideas? Why would the starboard pop out?

 

[ezeke]

Re: 1975 85 hp tillt and trim cylinder rebuild

Click the thumbnails, then print. Maybe they will help you.

The shuttle valve may be stuck; see the third thumbnail.

 

[beanutputter]

Re: 1975 85 hp tillt and trim cylinder rebuild

ezeke, thanks for the hyd schematic it was great help.

Now for the bad, system is still not working. I lowered both cylinders all the way manually, and then powered up, without the motor on them. The trim only cylinder does nothing until the tilt trim cylinder is fully extended, once the tilt trim cyl if fully extended the the trim only cly will extend about 3in. This is without the motor weight on it and I believe this is ok. Here is the problem when I try to lower the unit the trim only cylinder try's to extend while the tilt trim cylinder retracts. This results is the to fighting each other. The only thing I can see that would make a cylinder run backward would be the shuttle valve, but why would the tilt trim cylinder still work properly. The only other odd thing is that the tilt trim cylinder does not slow when it gets to the trim position.

I am losings faith and am getting ready to try to send the system back.