After sticking my fist through several inspection ports at West Marine I settled on the 6 port with the clear lens. It may sound stupid to try on several ports but I wanted to avoid the monkey fist full of cookies in the cookie jar syndrome. Whatever size port works for you MAKE SURE YOU READ THE INSTRUCTIONS!! Turns out the port with the 6 opening required a 6-1/2 hole saw. I didnt read the instructions so routing around the circumference with my trusty Dremel to achieve the additional 1/4 clearance is a bitch. After securely taping the port to the tank to hold it in place drill the 6 holes for the screws or bolts. Since the aluminum is so thin I opted for nuts and bolts rather than tapping and threading a bolt right into the aluminum. ONE THING TO CHECK is nut and lockwasher clearance on the underside next to the ports collar which protrudes into the tank.

Theres clearance for the correct size nut and washer but just barely. Plan on holding the nut in place with a wrench while you tighten the bolt head from above.

There really __IS__a thwartship baffle !!!

Before drilling with the hole saw make sure you accurately locate the baffle. Theres only on and its approximately at the midline. And its welded to the underside of the TOP of the tank.

In my case I thought I located it but I was off by about 1 when I drilled the cut-out. As a result I had to 1) cut down a portion of the baffle to have clearance for the protruding collar of the inspection port, and then 2) file away all the sharp edges. Youll appreciate the second step the first time you stick your arm through the opening. This may not look pretty but after the remedial cutting and filing it does the job.

That pink blob shown at the top of the photo looking through the port is winterizing antifreeze left in the tank. That will get pumped out once spring arrives and the threat of freezing is gone until next winter.

Make sure you sound where the baffle is!!!

I decided to add a sending unit to a remote gauge while I was in a cutting and drilling mood. As long as long as you have the inspection port and you can reach your arm down into the tank adding the remote sendor is a piece of cake. I didnt want to spend the big bucks with the Snake River unit so I called a few RV stores and found e-Components International as a source for water tank sending units. Dont use the Tempo fuel tank sending units!!!!! Theyre designed for immersion in gas or diesel. In a water tank theyll rust out and become useless in a few weeks. Contact me directly if youd like the contact info for e-Components International.

Might as well add a sending unit....