2000 C90tlry Yamaha Tilt/trim Won't Hold Position

[markernineteen]

This problem has gotten progressively worse especially in rough water. I have the shop manual and I've checked the manual tilt valve , bled the system and checked for electrical malfunction .I've disassembled the unit and everything looks perfect ! I bought this boat/motor used and from the looks of the tilt lock it has been trailered with the motor tilted and unsupported , could this be a factor? Is it possible the absorber piston on the tilt rod leaks internally ? Thanks very much for your help !

 

[rodbolt]

Re: 2000 C90tlry Yamaha Tilt/trim Won't Hold Position

ok drift down possible causes on the 6H1 unit.
bad up main valve,bad up relief valve,manual relese valve leaking,trim piston Orings are leaking,or the free piston in the tilt cylinder is leaking.

best I recall there is a good diagram in the service manual on the 6H1 system. this system was used on most the 2 stroke 70-90 HP motors for many years.

 

[markernineteen]

Re: 2000 C90tlry Yamaha Tilt/trim Won't Hold Position

Rodbolt you are a true professional , I've been a truck mechanic for 25 years and I can tell you really know your business . Since the trouble with my tilt/trim is not obvious to me I'll replace all the o-rings and seals associated with the parts you listed . Thank You ! Your help is greatly appreciated . MARKERNINETEEN