Access is actually quite good. All are under the sole. Just unlock and lift out a dedicated section for that purpose. Then unscrew access plate.
That’s not the issue rather was looking forward to pdq advice on best practices. Many boats top off where and when they can. Old is mixed with new. Boats commonly go quite a long time on a fill or top off. Especially where it’s windy. Sure you add biobor or like product but what else is advised to keep tanks clean, fuel that will burn nice and keep your engine happy.
There is no simple answer for keeping fuel fresh for >3 years, particularly when fresh fuel is being added to an inoculated tank. It's tough. The reasons trucks have fewer problems is that they burn the fuel!
I've done long-term testing, and although most fuel will keep in a sealed bottle for 10 years, some "turns" in a just few years under perfect conditions. If there is some air exchange, some water present, a few bacteria, and a few copper and zinc ions, the fuel is at high risk of changing in 3-5 years. The best you can do is:
* Silica gel vent filter. We can debate whether there is significant condensation, the fact of the mater is that the gel does absorb a few ounces per year. I think it is a good deal. Vent filters also reduce the amount of air moving in and out of the tank by convection (currents).
* Replace fill o-rings and put a little grease on them. If they are in a low spot, move the fill (I had a boat with a badly positioned fill that was in a rainwater path--it leaked no matter what and I moved it).
* Treat regularly with Biobor JF or any other biocide that is listed as a pesticide. I've tested many, and they all work. Biobor is my first choice. Do NOT wait until you have an infestation. Not only will you have to clean the tank, the dead bodies will go through your injectors, which is bad.
* Use double filtration, like a Raycor.
* Polish or don't. The evidence seems mixed (it treats the problem, but it's not clear it prevents the problem).
* Run the motor more. There is no substitute for turnover.
* To fill or not to fill. If you use a silica gel vent filter, I think there is no good argument in favor of filling. And the vent filter is cheaper than a fill-up!! Getting fresh fuel is better.
* Use a good anti-corrosion additive. It is the ions that make the fuel unstable (much testing, by ASTM, engine makers, and Practical Sailor).https://www.practical-sailor.com/iss...s_11083-1.html
* Avoid zinc and galvanized. Minimize copper alloys. I'm not sayin' rip stuff out... unless it is copper tubing fuel lines. The USCG got that all wrong, just ask the engine makers.