I am going to say NO. Unless you have some way of supporting the boom, so the weight is off the cylinder. I don't trust any hydraulic device for holding weight for any length of time. Best bet, be safe.
I don't like to tax the seals, so if I don't want to collapse the ram I support the boom. My old HF cherry picker is also slow to pump up, been that way for 20+ years and I've used it a fair amount that way.
Hmmm.... I replaced the jack on my engine hoist several years ago with a HF Pittsburgh jack. Seems to work as well as as the old one and doesn't require an excessive amount of pumps. Maybe I got lucky. And I have never left an engine dangling on a hoist, at home or at work. I just don't trust them.
Re: cherry picker engine hoist question - 01/01/2202:41 AM
Mine (from Kragan/O'Reilly's several years ago) will slowly go down so I never leave anything hanging. I also don't want any part of the piston exposed to moist air very long. Best to keep it down to avoid rust and most loss of seal.
I have a northern tool hoist(it sucks because the front wheels don't swivel) and when it is all the way down I can just lift the boom up and it will catch it. You have to lift it pretty far past the height you want or do it twice but it is way way better than pumping that whole distance. This obviously doesn't work with a load.
A friend of mine has the best cylinder for his and I need to replace mine with it. It pumps on the up an down stroke so if you are moving an engine from the ground to stand or install height its super fast. Its the only one I have seen that way and it is awesome.
I have a gantry crane I built, uses a chain hoist, though I could put one of those 110v electric hoist on if I wanted. It was built to clear the ceiling support beam in my garage. It can be built taller for the same cost. No need to pump anything on it.