[coastiechief]

I have a 1976 Grady White with a 165 HP I/O. The power trim does not want to trim down but trims up just fine. I bled the system IAW the mercruiser shop manual twice for the down and up side using new fresh power trim fluid. Fluid from bleeding appears to be milky and air is present in the system. After seven tubes of fluid and multiple bleeding I still have good up trim but it will not trim down and is in fact getting worse and only will trim half way down. If I crack a line and push the cylinders they will retract. I rebuilt these cylinders several seasons ago using new o-rings and resealed threads of gland nut with mercruiser perfect seal. The work I did to the pump at that time was disassemble, clean and install four new orings and a new seal on the tank. Having said this how do I determine if either the pump/valve body or one or both of the trim cylinders are bad. Can the valve body induce air even if the system is bled or can it prevent retraction but allow extension. I have tried to utilize the internet to answer these questions but none found. Thank you for any help you can provide.

[MikeW]

Hello Chief, sounds like the pump is working or the unit would not lift at all. You are having a problem with the Control Valve. Some people refer to it as a Valve Body. They can be rebuilt. Give Go2marine a call and they can arrange it for you.

[rick24]

I have the exact same problem on my 2001 Rinker . Did the new valve body take care of your problems ?

[fourfather]

I have a 1975 Mercruiser 165 I/O with a power trim unit that works erratically. One cylinder works about 60% of the time, the other only about 10%. In both cases they go out better than in. The fluid has quite a bit of air bubbles in it. Any idea what might be the cause?
Also, I've heard and read lots of differing opinions on what fluid should be used. 10W30, Dexron, power steering fluid, etc. This unit had a clear fluid in it that appears to be power steering fluid. What is the proper fluid to use?
Thanks for your help.