You're facing exactly the same question I had earlier this year.
I started out, just like you, thinking about leaving well enough alone. I was not aware that there was anything particularly wrong with my VHF installation
Then as I gathered information from the thread which Saltyhog has linked above, I decided to rip it all out and do it over again, carefully. The results were unbelievable. You can read about that here: Amazing Power of Good Antennas
My advice to you, based on having just been through the same exercise:
1. Rip it all out and throw it away.
2. Choose a really good antenna -- one which is an internal dipole, and not a steel
whip. Here is the one I used: Shakespeare Galaxy XP High Performance Antennas
. It is really good, but it has one disadvantage: it has a pigtail for the antenna instead of a socket. You might check around for Procomm or Banten professional antennas which might be even better. Don't save money
on the antenna -- the most expensive ones are still less than $200, which is chump change in the grand scheme of things. It makes a huge difference.
3. Use low-loss cable. RG8X is the best thin type; if you can pull thicker cable then use RG213/U or RG214, preferably the kind with tinned shield and conductor. Some people advocate foam-dielectric cable like LMR240 or LMR400; I have avoided it since it is traditionally considered to be vulnerable to marine
4. Use good connectors, installed well, and the fewer the better. A Type "N" at the antenna (if it's a type which has a socket for Type "N", like one of the Banten ones), is ideal. If you use the Galaxy like I did, you will have to cut off the pigtail and install a socket on it. I used Type "N"s there and recommend you do the same. Other people will tell you that the more traditional "UHF" connectors (SO239/PL259) are good enough, but no one disputes that Type "N" is better in every way, so why chance it?
5. Unless you have your mast out often, don't put conectors at the mast base -- just run the cable all the way from the masthead to the nav table. If like most people your mast is not out more than once in 10 years, you will want to replace the cable every time anyway.
6. In my opinion -- and others will no doubt disagree -- the best way to install coax connectors, especially Type N connectors, is by crimping, not soldering. For that you will need the expensive special tool, or you will need to hire a pro. My reading shows that although soldering is the traditional method, it is notoriously hard to do right, and even when done apparently right, tends to melt the dielectric in the cable. I say -- just crimp it.
7. Connectors at the masthead will need to be carefully weatherproofed. There are different ways to do it. The best way is probably self-amalgamating tape covered then with adhesive
shrink wrap tubing, but you can also electrical
tape over the self-amalgamating tape (that's called a "telecomm wrap").
8. Don't make the mistake I did and fail to test the installation
before the mast goes back up. I screwed up one of the connectors at the masthead, which I discovered only after the mast went back up.
It may sound like a lot of trouble, but it is really, really worth it. Good luck!