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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4725
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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I have an old 1979 Mercury Inline 6 cyl, 140 hp. that runs

Customer Question

I have an old 1979 Mercury Inline 6 cyl, 140 hp. that runs great, the power tilt lifts and lowers the engine fine, but it leaks down from the top position in about 4 min. to the bottom of it's travel. The engine ser.#5433701. I have told it be that the two lift cyl. are by passing fluid, the orings in the valve assby could be bad or the control valves may be leaking. There are no external leaks of oil from any of the lines,pump,valves, nor anywhere
else that I can find. Where do you think the problem is? Thanks Tom.
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.
Typically a leak down like yours is in the valve body. Mercury does not provide instructions or parts for the valve body. However what I would do is to disconnect the trim motor electrically. Remove the 4 hydraulic lines from the valve body. Put a large pan under to catch the fluid.Remove the small screws on the bottom of the valve body to the resevoir.Remove the valve body.Using some spray carb cleaner clean out the valve body. There is a small silver cylinder, carefully remove it and clean the filter underneath.What happens is the trim fluid gets old and there is some trash build up. This holds a check valve open. Do not disassemble the interior of the valve body as there are no breakdowns of the parts and where the check balls go! Some of the torque screws adjust the pressure so don't take them out.Once everything is clean put it back together and see if it holds.Let me know how it goes.
Customer: replied 1 year ago.
Sorry but I have not had time to work on the engine yet, I will let you know when I do get to it. Thanks Tom.
Expert:  Jeff G. replied 1 year ago.
OK Tom, just let me know.

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