1980 Mercruiser 165 will not go down.

MC-1 with Prestolyte trim pump

1. Trim motor will turn on in the up and down position
2. I've disconnected the hydraulic lines at the cylinder on both sides and confirmed fluid is being pump in the up and down position and that they are in the right spots.
3. The outdrive will go up perfectly with no problem.

I have searched for a few hrs now to find a hyd diagram to see if there is a valve or some thing that would stop fluid from returning to the reservoir when down is selected but can't find one.

I check out the reverse lock (or whatever its called). I the control lever in reverse and was still able to trim the drive up but not down.

Am I missing something simple!?

Don, I am sure you can help me with this. Either by directing me to a diagram or have experienced this before!

Thanks in advance.

Re: 1980 Mercruiser 165 will not go down.

This should cover it. http://www.4shared.com/office/iUNMuxIG/04__Drives_120-260__78-82.html?

Re: 1980 Mercruiser 165 will not go down.

You are awesome Don! I am downloading now and I'll see what I can come up with. Have you seen this problem before?

Re: 1980 Mercruiser 165 will not go down.

albtross said:

You are awesome Don! I am downloading now and I'll see what I can come up with. Have you seen this problem before?

Click to expand...

Looking through the diagram and reading it seems like there is some valving inside the valve body and pump assy. It's funny because looking at these parts reminds me alot of what is on our old C130 Hercs for valve housing on the Props!

I'll let you know this week how I made out when I take it apart and clean it out!

Re: 1980 Mercruiser 165 will not go down.

So I took the control housing apart and cleaned it up and made sure all parts were clean and moving. There are quite a few bearings and springs inside. The shuttle valve I could not get removed but was able to get brake cleaner inand blow it back and forth with compressed air. This shuttle valve is what allows return fluid back to the reservoir. there was some milky oil in teh valving so I figured I must have found it but to my surprise it still will not go down. I am going to remove, tear down and inspect the 2 trim actuators next. It is about the only thing left that it can be. I haven't had a lot of time to wotk on it but tomorrow morning I will spend some time with it

That's the update so far.