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I have an 86 150hp Merc with tilt/trim that has stopped holding the engine. The engine will slowly 'fall' down over a period of a few hours if I do not lock it in place. This has only been going on for a few weeks. Prior to that it was working fine.

I know nothing about how tilt/trim works. I assume this mean I have a leak somewhere? I do not see anything leaking, but really do not even know where to look.

Any ideas about how to trouble shoot and how to fix would be greatly appreciated.

Graham

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All the Merc folks must be gone today.

I would first check the fluid level in your Trim & Tilt system.
If that is fine then I would say you have an internal leak within your Tilt cylinder and that would possibly need rebuilding.

I am not a Merc man so maybe other Merc owners have more info for you.

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Yes, it does sound like a leak. If you don't see and fluid leaking then as Joe said it could be internal. Merc pump motors are not cheap and I have never seen an aftermaket one. Odd design. They can be rebuilt though. Just seals.

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Graham

I had a V6 like this. The PT did have an inherent problem. Mine was ultimately fixed with a newer style power trim system introduced in the late 80"s. It fit perfectly. Never an issuse after that. I sold it in 2005. I had an extended warranty at the time and even wrote to Mercury over this problem in 86/87....

I assume you have the original PT system? My problem was that it would not stay up past the the trim point. I needed it to operate the outboard past the highest trim point order to troll out of a cove where there were submerged stumps. It would slip down even running at 900 RPM. It was brand new at the time. The seals just could not hold it.

Naturally like other suggest check the fluid in the system... and the seals do go bad which will make this issue much worst.

This does sound like seals if the engine does not stay up just sitting. Fluid must be leaking past the seals...

Hope this helps...

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more information.

I just went out to take another look.

The retaining ring, washer and scraper are all able to move up and down on the rod. This leads me to believe that the retaining ring is not doing a very good job retaining.

I still dont see any fluid leaking........

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My brother works at an electic motor shop. Take it apart and bring it in. They can change all the seals for you.

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I see that your last post was a few months ago,so I don't know if you figured it out yet. This weekend I changed the trim seals on my Yamaha and noticed that the manual relief screw was not fully closed. I had a sinking problem also because of the leak and the screw. I don't know if Mercury has this manual relief screw but its worth a look see.

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thanks Paul-

I had a friend also suggest checking the manual relief screw. Will definitely check it out.

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update:

I think it was the manual release valve. Tightened it and it seems to be holding.

this is great news. thank you for the help.

According to the manual, to rebuild the tilt cylinder, you need to take the engine off!!!