Systems & Propulsion

Fueling a boat has never been as easy as fueling a car. Spills-exacerbated by poorly designed fill pipes and vents-are common. The U.S. Environmental Protection Agency (EPA) has updated the fill and vent requirements on boats to prevent these spills, but they only apply to new gasoline-powered boats. New jerry cans designed to prevent spills and comply with new emission standards arent making things easier. Most are hard to control and slow during filling, spill prone, and break after limited use.

If we used our boats like the family car, back and forth to work each day, fuel would never sit for more than a few weeks and it would never age. Instead, boats sit for weeks at a time in-season, and for months during the off-season. Water, oxygen, bacteria, metal ions, and even instabilities in the molecules themselves combine to turn fresh fuel into a soup that will clog filters, corrode fuel systems, and leave us stranded. Fuel refineries have long known this, and all products are dosed with inhibitors at the refinery; however, these dosages are calculated for the normal distribution and storage times, not half-full tanks that will sit for months or even years.

We followed standard test methods for storage stability. Diesel was tested using ASTM method D 4625, Standard Test Method for Middle Distillate Fuel Storage Stability at 43C. Samples were exposed to air for up to two years at 113 degrees (45 degrees Celsius); each day simulated about four days of real-world storage, according to industry experience. We settled on 8 months of exposure, the equivalent of about three years. At the end of each period, samples were filtered, and the insoluble solids weighed.

Sometimes it is not what has been added to your fuel that matters, but what is missing. The most obvious difference between gasoline and diesel during our vented, fuel-aging tests was that gasoline samples evaporated and required replenishment at the mid-way point; diesel samples did not. Studies by BoatUS and the U.S. Environmental Protection Agency (EPA) have shown that anywhere between 5 and 20 percent of the contents of a portable or installed polyethylene gas tank can vanish in one year through evaporation and permeation. The remaining fuel is lower in octane, contains fewer of the volatiles that are so essential for easy starting, and has reduced solvency for gum and varnish. It often looks perfectly good-most of our samples did-but it is perfectly rotten and potentially harmful as fuel.

In our recent test of absorbed glass mat (AGM) batteries, we cycled five different batteries through 30 deep cycles to 11.7 volts but only partially recharged them for one hour after each discharge cycle at a charge rate of 46 percent of battery amp-hour capacity. (See PS May 2015 online.) The object of the exercise was to demonstrate just how quickly sulfation, which is caused by keeping a battery in a partial state charge (PSOC), can reduce the capacity and eventually permanently ruin a good battery.

Our May 2015 report on absorbed glass mat (AGM) batteries got us thinking about wet cell-batteries. While it is easy to find distilled water suitable for topping off the battery electrolyte in the U.S., what happens when we are not near a reliable supply? Are there any substitutes? What should we avoid?

Only a few states require National Sanitation Foundation (NSF) certification for water filters, and the requirement applies only to a small number of original equipment manufactured (OEM) products.

Foul tank water is completely preventable. Here are some dos and don'ts for a healthy water tank. Dont place glycol or other winterizing agents in the tank. Install valves as needed to winterize the pipes only; typically a tee and two valves located near the tank drain work fine.

Leave water from any source in a storage tank for a while, and interesting things will start to grow. Only the purest water in an airtight bottle will have a long shelf life. But not all bottled water is what the label says it is. For a cruiser, there are two water-testing tools that are important, and a third tool that is helpful in determining what is going into a tank and managing the quality of fresh water on a long-range cruising boat.

I just received the latest Waypoints e-letter about gel batteries, where you state they must be charged at no more than about 14.1 volts. We do not use gel batteries in our boat, but do in our camper van. As I understand, Trojan deep-cycle gels can be charged up to 14.4 volts and East Penn marine gel batteries up to 14.6 volts, so why are you recommending the lower voltage?