Trim and tilt problems 90Hp Yamaha.

[Mieliepit]

Hi there, I hope someone can give me some advice. The trim and tilt motor on my one motor keeps falling down slowly (Yamaha 90hp). On the trim and tilt unit is a number 6H1-13, I am not sure what it stands for. I have changed all the seals on the trim piston assemblies,tilt piston assembly and on the manual release valve. When this problem started I suspected the manual release valve.The two flat seals (Seats) where in bad shape so I thought I have solved the problem by replacing them but it is still doing it. If I cycle the motor up and down a couple of times it will stay up, but I haven't tested it on the water under pressure and I am sure it will still push the motor down. If you look at the first schematic (Manual I have) it shows a different type of manual release valve (Items 10,23,24,25,26,27,28,29,30,31)and I don't know why. The manual release valve setup in my trim and tilt motor is the same as the one in the second schematic.(Found on net) I have replaced the two seats (Item 60) but my setup has a extra spring a little bit thinner than the other spring(Item 61)between item 62(Adapter) and item 60. In other words it has a spring on both sides of the adapter (Item 62), could this be my problem? If not what would you guys suggest, where do I look for the problem?
Schematic 1.

[boats.net]

May have any of releif valves or main valve leaking, start by check mains, number 30 in scond diagram.

[Mieliepit]

Thx for your reply. I will do so and give feedback. It seems as if lots of people have the same problem and nobody realy knows what causes it.

[robert graham]

Thx for your reply. I will do so and give feedback. It seems as if lots of people have the same problem and nobody realy knows what causes it.

My 1999 Yamaha 90C tilt/trim leaks down slowly, but not a huge problem...guess any hydraulic system with multiple valves, seals, O-rings,etc. may develop leaks sooner or later. I believe these tilt/trim systems are fairly complex and require special tools and expertise to rebuild. Good Luck!

[ken52]

My 99 Yam 150 did the same. What I found is I had to go through the bleed procedure a few times and keep topping off the fluid. Once I did that it didn't move. I was told from a dealer that if the boat sits alot you get some bypass of fluid. And he said to take it out and run it up & down a few times. Mu best results was doing the bleeding procedure in my repair manual. Good luck.

[Tgsx750f2000]

I have a 1999 Yamaha 90hp two stroke that was doing the same thing. All I had to do was unscrew that flat head screw that let the motor come done a couple times and tighten it back up and it stopped. Must have had some trash or deposits on it.