I have a Vermeer V-1150 trencher and the boom will not go up or down without someone helping it by pushing down or pulling up. Everything else works fine.

https://www.vermeer.com/LA/en/N/support/safety/product_manuals

Best Manuals Guess you should try one of these ebooks. It's very helpful, I use it too

Loosen the fitting at the hydraulic cylinder, start unit loosen fitting bleed till no air comes out.

Craig, I do not have a lot of experience with trenchers, if hydraulic operated not enough oil/check reservoir,, one of the valves/controls may be stuck, you will have to follow line from boom cylinder and trace it back to the valve and dismantle and repair. Secure boom as to not harm you or others.
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Check the fluid level.

go to Best Manuals

Find the serial number and model number. Give Vemeer a call and they will be able to give you the part numbers. Probably give you a schematic as well.

there's a website that has all this information and manuals everything totally free there are many actually but I personally like few .. let me know if u need help
thanks

Go to Vermeer.com and put in the model number and serial number. Vermeer will send you an operaters manual, parts breakdown and repair manual for free.