Alternator to battery cable fuse needed??

Newbie here and could use some advise. I recently replaced the alternator on my '92 Lesabre and upgraded from the CS-130 unit ( 105 amps?) to a CS-144 with 140 amp rating. The advise from the online seller was to upgrade the wire size from the alternator to the battery to accomodate the higher output alternator. That advise and the fact that the factory alternator wire lug wasn't big enough to fit on the CS-144's larger output stud, led me to use a 4 ga. batery cable as substitute. The factory wire looked like about a 10 ga.

I have read somewhere that this wire should be fuse protected, since I bypassed any fuse protection the factory wiring had. I'm not the sharpest knife when to comes to electrical matters. Is fusing this cable necessary? It is strictly from the alt to the battery. The factory cable from the battery to starter is in place.
If so, what type and rating of fuse should I use. About the only type high amp fuses I have found on the Web are ones used for big car audio amps.

Also, with the new alternator, I've noticed that when the car is started, it takes about 3 seconds for the alternator to kick in and for the voltmeter to jump up where it should. I don't remember the old unit really taking any time at all. Is this the sense circuit doing it's job or not doing it so well?

Thanks for any input! I enjoy the AF forums and have been helped numerous times by other posts.