Some thoughts on consumption as you mentions on your site going a "couple of days"..
As others have said...battery monitor first.
The Victron BMV-601 can be had for under $200.00 but this is still double the $100.00..
The below calculations assume a 60% cycling of the fridge at 5 amps. This could be less or more depending on insulation. The 25 Ah number could be very slim depending upon what you use, you may use more or less:
@60% cycling / 5 amps draw = 72 Ah's / 24 hr
25 Ah's / 24 hr
TOTAL / DAY = 97 Ah's
97 Ah's X two days = 194 Ah's consumed
If you want to run two days at the above loads before recharging it looks like this:
194 Ah's needed... so.... GULP
650 Ah bank depleted to 50% DOD = 325 usable Ah's. (This is ONLY when the batts have been FULLY charged to 100% SOC)
Real world on the hook cruising:
650 Ah bank only recharged to 80% while on the hook charging by alternator is:
650 @ 80% of full capacity = 520 Ah bank
Depleted to 50% of total bank capacity of 325 Ah's leave you at:
520 Ah (80%) - 325Ah (to 50% total bank capacity) = 195 Ah of real usable battery capacity.
To use 194 Ah's over two days with no charge time in-between you'll need a 650 Ah bank to do that.
Using West Marine deep cycle group 24 batteries @ 75 Ah each it would require 9 group 24 batteries.
Using Sam's Club 6V golf cart batteries it would require 6.
If you plan to recharge every day cut the above number in half, or a 325 Ah bank. Only do this if you will be able to run the motor long enough to replenish the bank to 80% which can take many hours.
Of course a battery monitor may tell you that you only burn 72 Ah's a day. Guess work can be expensive and a good monitor can pay for itself if you were to over buy/build a system.
If using wet cells plan on max acceptance of about 25% of Ah rating so. Most recommend an alt of 20-40% of bank capacity.
650 Ah bank = 162 amp alt: This is not going to happen easily on a small motor so charge times to 80% will take a while.
325 Ah bank = 81 amps This is achievable on a small motor with a 100 amp alt.. Going bigger on the alt is fine as it works it less hard and never puts out full "spec" when hot..
Disclaimer: These number are all rough GUESSTIMATES but the basis for bank sizing theory is what you really want/need..