What kind of electrical outlet is this? Red, winking-face shape
The formal technical term is Ms. Winky (sockets are female)...

That is a NEMA 6-20. It provides 240V at up to 16 amps continuous.  The fuses must be 20A, that is the only size allowed here.   

As a general rule, you can never give yourself more power by up-sizing fuses or breakers, so put that idea right out of your head and never consider it again.  It's not like we randomly use excessively large wires for no reason.  Fuses and breakers are already the max the wires will allow. 

There is no neutral here, which means you cannot derive 120V except with a transformer.  You cannot take neutral from anywhere else for a variety of reasons.  However if the cable supplying this outlet also includes a (capped off) neutral, or if the wires reach this outlet via conduit, an upgrade is possible - ask.

Also as a general rule, any load that requires 25A @ 120V (3000W) is very stupid.  That's not how power is done in North America.  Common receptacle circuits are 15-20A.  The vast majority are 120V (permitting 1440-1920W maximum (80% is the max for a plug-in appliance).  However, 240V is well supported, giving 2880-3840W maximum.  Therefore: Any appliance that needs 3000W would be manufactured to use 240V.  

You are keeping your load a secret, so we have to guess. You say it needs 25 amps (3000W).  If it is an array of PCs or other load that is capable of running 120V or 240V, then you are in luck.  You can get 4800W (3840W continuous) out of this receptacle.  Just get a NEMA 6-15 power strip and cords and you're off to the races (6-15 is more readily available than 6-20).  

If your load absolutely requires 120V, then buy a different thing, or  get an isolation transformer (not a stepdown transformer) of appropriate size.