Power Trim slowly lets motor down

Fish Head	I have a 100hp Mercury on my 17 ft. Sea Ray. I noticed the motor will slowly lower itself from the up position when on the trailer. Takes several hours. I can't find any hydraulic oil leaking from the unit. What would cause this to occur,could it just be low on oil? Just bought the boat hope its nothing major. The PT/T works fine otherwise.	2002-03-18
MIKE F	My GUESS would be that the fluid is low or the relief/release screw on the unit is not tightened all the way.	2002-03-18
f_inscreenname	The pump is bad. The same thing happened to me 2 years ago. When the pump is not powered it lets fluid pass through it(the ball cock I think) when it should'nt.You can rebuild but I don't think its worth the time. M	2002-03-18
jocko_nc	I assume this is an Oildyne, Teleflex, or some other copy of the Oildyne. If the pump is shot, the unit will not lift when running. If the check valve is leaking, it will slowly settle. The two functions are independent. The pump generates flow, the check valve stops internal leaking. Follow the hydraulic line from the lift side of the ram. There will be a SMALL pilot-operated check valve machined into the valve body where the line goes in. This should be a small ball, dart, or poppet of some type held closed by a small spring. Sealing depends upon a machined metal to metal fit. The sealing surface might be dirty. Clean it. You might "coin" the two surfaces together if there is an irregularity. You should have relief checks built into the the ram piston itself. This is supposed to relieve pressure shock in the event of a "log strike". Leakage here would cause drift. Leaking piston seals would do same. Hydraulics 101. Good luck. Jocko	2002-03-19

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