1972 MC-1 Water in hydraulic trim system

[998cc]

Hello all. I took the boat out yesterday, and at some point, a hydraulic hose literally popped off the fitting at the trim cylinder. It failed to raise at the dock, and I had to manually raise it to get it on the trailer. There is now water in the hydraulic system that needs to be drained/flushed. I flushed out the trim cylinders but would like your opinions on flushing the rest of the system. Can the system be flushed without completely disassembling it?

 

[wahlejim]

Yes it can, and it would be fairly easy if water has not made it back to the reservoir. If water has made it back to the reservoir, I would pull it and clean the reservoir before flushing the system. It is really easy and might take all of 30 minutes from start to finish. If you have to take the pump apart, do NOT take the valve control body off of the bottom of the pump. You will have to replace 4 o-rings inside there if you do.

Otherwise to flush the lines:

I would usually tell you to start with the rams in the down position, however if you sucked water into the rams when you manually lifted it, I would not advise that. Lowering the rams with the hoses connected using the trim pump would force any water in the rams back through the system and into the reservoir. Just by undoing the up lines, the rams should lower themselves. Make sure you have a bin underneath the system to catch the oil. Disconnect the up lines and run the system "up" and watch for clean oil to come out. Repeat with the down system.

Here is a link to the hydraulic schematic on an MC-1: http://boatinfo.no/lib/mercruiser/manuals/mercruiser4.html#/134

Read through the entire section to see what you are dealing with before you start. Bleeding procedures are in there is well if you have to take the rams apart.


If you think there is water in the rams, take them off and disassemble them, clean them out, re-assemble, and bleed the system. This is really easy on the MC-1 system. The first ram might take you 45 minutes as you are learning it, but the 2nd one should take you under 20. It will be a never-ending cycle to get the water out of the rams without taking them apart.

IMHO, there has to be a reason that hose popped off. You need to diagnose that. Possibly stripped threads on the housing of the ram? You can buy just that housing for relatively cheap. Mercruiser # 77442A1

While you have it apart, you can change the seals as well. The whole kit is just a bunch of o-rings. Merc 25-60342A2

I have torn my entire system apart this summer and re-built it. If you have any questions, just ask.

 

[998cc]

Thanks Wahlejim. I am fairly sure water is in the pump reservoir, so I will pull the whole system. I agree that it is a good idea to open up the rams. I have a spare set of rams in the junque box that will get re-done at the same time.
The "up" hose completely separated from the stainless fitting. No thread iussues at all--just a failure at the crimp connection.