summation:
Prevent by controlling
condensation by keeping tank full.
Polish your own fuel with water separating
fuel filter and
electric pump.
Treat fuel before you store for
winter, and while allowing air pressure
changes, limit air transfer by using a flexible bulb and "blocking" air exchange from the vent for
winter. Empty the bulb of fuel as it will have water in it. Expansion and contraction from a small tank will be minimal. Some tanks flex enough. Know your situation. Think it through. Treat for the bacterial and algal growth. Test the fuel and restore your fuel and system before you use the
boat. I have run engines on boats that recirculated 800 to 900 gallons of fuel ever 3 hours, and polished it using only the
engine driven fuel pumps. That fuel became warm from
engine heat in 4 or 5 hours. Dual water separating Racors did the trick. Tanks could be run separately or linked, and return fuel control was a science. Fuel system was a special one and required 3/4 inch fuel lines and valves. Not
Yanmar engines. Cummins. Some of those engines are still made with
bronze plates autographed by the crew that built them. Turbos the size of small truck tires. Not
cheap, but a pleasure to run!
Any diesel engine needs clean relatively dry fuel and no water block or dirt to foul the injectors! Plenty of air and enough water to cool engine and
exhaust... lubrication. A diesel engine is a thing of beauty! I love each and every one of them!