1996 Mercury 150 EFI - Tilt cylinder not holding pressure.

Theoutdoorsman

Theoutdoorsman

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When I tilt the outboard all the way up (or any height above full trim) the tilt cylinder will not hold the outboards weight. It will slowly fall until it meets the trim cylinders, at which point it will hold. I need to check the fluid level to rule that out. Is this the fill screw for the system? I'm pretty sure I know the answer. I would just like to be sure before randomly turning screws. I'm assuming it's full when it runs out the top with the outboard at full tilt, correct?

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Theoutdoorsman

Theoutdoorsman

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Theoutdoorsman said:
When I tilt the outboard all the way up (or any height above full trim) the tilt cylinder will not hold the outboards weight. It will slowly fall until it meets the trim cylinders, at which point it will hold. I need to check the fluid level to rule that out. Is this the fill screw for the system? I'm pretty sure I know the answer. I would just like to be sure before randomly turning screws. I'm assuming it's full when it runs out the top with the outboard at full tilt, correct?

View attachment 409521
Click to expand...
 
Theoutdoorsman

Theoutdoorsman

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Also, can I use the tilt n trim fluid at the local wally world in this system, or?
 
Theoutdoorsman

Theoutdoorsman

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Ok .... I removed the fill cap and, to my surprise, the system was full of fluid. Really was thinking it'd be a little low causing the slow fall at full tilt. The outboard trims up/ down just fine. It just won't hold it where I stop it. I'm thinking a bad internal seal? Any ideas?
 
Scott Danforth

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or the hydraulic piston seals which last only 15-20 years need to be replaced.
 
Theoutdoorsman

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dingbat said:
Or a bi-pass valve is leaking.
Need to tear down and inspect
Click to expand...
How do you remove the pressure relief screw to inspect the seals on it? Figured I'd start there before tearing into the cylinder itself. I can see a "C-clip" around the head of it. Not sure if that must be removed before it can be taken out.
 
Theoutdoorsman

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Scott Danforth said:
or the hydraulic piston seals which last only 15-20 years need to be replaced.
Click to expand...
Amazon has a seal kit for the system. It's cheap enough, but I'm not sure I'll go that route. Pretty sure there's a company out of Florida called 5-Star that sells a seal kit comparable to OEM. I'd have to research more to find a part number on the kit I need. The serial number on the outboard is 0G424278 of anyone knows the part number on the required seal kit.
 
Theoutdoorsman

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Scott Danforth said:
I use Five Star myself
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This system is totally sealed. It has never leaked a drop, and never seen salt water. If you had to guess, which seal in the tilt cylinder would you suspect has failed that would cause these symptoms? Curious if there is a common seal failure point that may be suspect.
 

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Scott Danforth

Scott Danforth

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All of them need replacing. However the piston seals are probably bypassing if the cylinder doesn't hold load

The materials used in the seals last about 15-20 years max and then they break down
 
dingbat

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Theoutdoorsman said:
This system is totally sealed. It has never leaked a drop, and never seen salt water. If you had to guess, which seal in the tilt cylinder would you suspect has failed that would cause these symptoms? Curious if there is a common seal failure point that may be suspect.
Click to expand...
All seals harden and deform overtime.
Its not if, it's when......

Doesn't make sense to tear it down and not replaced everything while you have it apart..
 
Theoutdoorsman

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Tilt cylinder seals replaced. All of them. Still slowly losing pressure. I'm stumped!
 
Scott Danforth

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Did you nick a seal when reinstalling the piston? I myself nick one out of every 6 or 7 cylinders
Easy to check
 
Theoutdoorsman

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Fluid level is good. I still see air in the fluid if I crack the the fill screw loose. Maybe it's just gonna take time to work it's way out?
 
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