Tilt/Trim slowly leaks down 90HP 2 stroke 2002

[jelanier]

Tilt/Trim slowly leaks down 90HP 2 stroke 2002

I have developed a problem with the Tilt/Trim not holding position. It slowly leaks down. I have no fluid leaks and T/T works up and down. Fluid level is OK and fluid is clean. There must be a bad O-ring that is bad causing internal pressure equalization. I am new to this but I would guess that it is associated with part 39 (2 of them). Maybe even parts 50-57. Could someone explain the purpose of those valves? I know 50-57 is the manual release. I am not sure about 39.

Thanks in advance,

Jim

[jelanier]

No one knows? I guess I am on my own on this one.

Jim

[fairdeal]

perhaps Rodbolt is on vacation - hope whatever has him away is good, anyway

40 is the "shuttle valve" - I believe essentially a "check" valve that allows pump output

somewhere in there you have one or more "relief valves"
and a "memory piston" in the tilt cylinder
I imagine just about any of the seals/o-rings could cause leakdown if worn

I don't think you can decide in advance which part you are going to replace;
either buy them all (does Yamaha package a "seal kit" ? don't know)

or prepare to tear it completely down and decide then what you will take a chance to re-use

[panasonic]

Do you have a service manual for your engine? There should be a flow schematic in the manual showing all the check valves and spool valves in the trim tilt assy. There are many orings in that unit and almost any one being bad could cause it not to work properly.

Have you removed any of the valves that are accessible from the outside of the unit and inspected them for a cut or worn orings?

[panasonic]

I myself would invest in a SM before picking it apart. Trim units are very expensive and SM are not.

[fairdeal]

here is a "typical" t/t functional schematic - perhaps not exactly your model





I can recall my astonishment upon first reading an outboard shop manual -

and discovering that the t/t unit was more complex, and had more moving parts,

than the 4-stroke engine to which it was attached

[jelanier]

Thanks for the replies. I have not taken any of the valves out yet. They are all inaccessible without removing the TT unit.

I have ordered a service manual. I am going to order all of the o-rings for those 3 valves and replace them. It looks like 7 rings in all (40,41,37,40,41,54,56). It looks like a lot of work to remove the TT unit. I don't want to do it twice.

Thanks,

Jim

[panasonic]

That sounds like a very good plan Jim.

[jimbliss]

I had the same problem with an 04 90hp. After flushing and changing the hydraulic fluid it stopped leaking down.

[fairdeal]

I had the same problem with an 04 90hp. After flushing and changing the hydraulic fluid it stopped leaking down.

I can believe that - a piece of schmutz in a critical spot could be the problem -

might be worth trying before going the whole route to remove and dis/reassemble...

[jelanier]

I had the same problem with an 04 90hp. After flushing and changing the hydraulic fluid it stopped leaking down.

OK, but I don't know how to flush it other than opening fill hole, lowering to overflow raise and fill. Rinse lather repeat. Is there a way to circulate new fluid? Maybe opening the manual release and running the T/T motor in each direction would accomplish this?

Jim

[99yam40]

I agree no way to drain it, much less flush it

[rodbolt17]

leak down

up main valve
up relief valve.
manual valve.
trim piston orings.
free piston.
take your pick.

[panasonic]

OK, but I don't know how to flush it other than opening fill hole, lowering to overflow raise and fill. Rinse lather repeat. Is there a way to circulate new fluid? Maybe opening the manual release and running the T/T motor in each direction would accomplish this?

Jim

I would think that loosening item 34 or 33 (hyd lines) at the bottom of trim/tilt unit and operating the trim/tilt would allow the fluid to come out.

Don't run it dry...drain some out, refill reservoir, drain....ect.

Watch out as I don't how much pressure is there at these lines...wear safety glasses!!

Make sure tilt locks are being used as well.

[99yam40]

Have read about people buggering up the lines trying to take them loose. be careful and use the correct tools if you try