If you have a 64-bit OS, you could try this:
Windows10; Large Address Aware; SH4 Install - CapnScurvy speaks specifically about a Windows 10 install, but any of the other 64-bit Windows is very similar. He installs Silent Hunter 4 and LAA (Large Address Aware), to set the SH4.exe file. It allows the game access to more than 2 gig of RAM (or rather tells the OS it can address more properly), and that will sometimes - sometimes, not always - let the game run smoother. If you have a 32-bit OS and more than 3 gig of RAM, let me know, and I'll accelerate my tutorial for that. I have had success with Windows XP 32-bit, but I still have to try things out on Vista and Win7 32-bit, to see if similar is available, but I'm lazy right now, and the Vista machine is sitting in the corner unplugged, missing a hard drive... does not look good...