How do you adjust this setting

[1977 SILVERLINE]

I have a 1977 mercruiser and I am wondering how to adjust the adjuster underneath this plug and what is it's purpose? It seems to affect the trim motor. The farther I turn the adjuster in the harder the trim motor has to work to lower the drive. I have already messed with the settings so I would like to find out how to adjust it correctly so I don't break anything. Thanks

 

[1977 SILVERLINE]

No Title

Picture didn't post but here is the part number and description. CONTROL VALVE ASSEMBLY 48077A3 There is an Allen headed plug on this addy and behind that plug there is an adjusting plug that I'm unsure of its function and adjustment procedure. Thanks

 

[Fun Times]

I've never messed with one of these myself! Are you able to find any information about this in the OEM service manual?

I found a bulletin while looking up the part number you provided. Just thought I'd share it with you. My first thought was they should have been set from the factory and if you had a problem with it, a new one would help solve the problem. That was always the service recommendation with the later model trim pump control valves anyways.

http://boatinfo.no/lib/mercruiser/manuals/mercruiser4/pages/page_h222.swf

 

[Bt Doctur]

Why would you even go there, let alone start turning things? There is no procedure for adjusting the valve body.

 

[UncleWillie]

Assuming you have just turned the pressure regulator...
You will need to place a pressure gauge in line with the hydraulic hoses going to the trim cylinders.
Then, while operating the pump, adjust the regulator to the specified pressure, typically around 2,200 psi.

This is a factory adjustment and should never need to be touched, especially on a 37 year old pump that is no longer available.
Unless you have the means to re-adjust it properly, adjust it to the point where you remember it sounded, and hope for the best.