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Back some twenty years ago gasoline was much different from what we have today. Through the early 70's it was cheap and plentiful. The formula for making gas was the same year to year. Lead was added to the gas to better its quality. As far as the engine was concerned lead worked great. Large powerful engines ruled the roads and lasted what seems like forever.
The gas of twenty years ago also created severe problems. Many cities suffered smog. The lead did not burn during engine combustion. It passed through the exhaust system and was deposited on roadways. There have been many reports of lead causing serious health problems. It was past the time for a change.
The gasoline that we now use is part of the answer to yesterday's problems. Lead is no longer used. Today's gas formula has reduced the pollution problem. New additives allow for the building of cleaner burning, fuel efficient engines. Sadly, there isn't a good comment to be had for the price of gas.
Along with the great improvements in gas technology come a handful of new problems. Taking lead out of gas reduced it's octane level. New chemistry was introduced to gas to boost the octane rating. Other additives were used to help gas clean the engine internally. Fuel was extended with grain alcohol to combat the rising prices. Some of the gremlins created by these changes are probably going to stay with us for some time.
Gasoline has always had a limit on how long it lasted. The boosters and additives used today do not last as long as before. Alcohol based additives evaporate much more quickly. The latest figures given for the shelf life of gas is sixty days. Day one starts when the gas is made. If you put gas in your boat that was made a few weeks ago you might be left with forty days shelf life.
The biggest problem with old gas is that it will loose octane. Using gas with a too low octane rating can destroy an engine. The burning of such gas is uncontrolled (one of the main functions of an engine is to completely control the burning gas). The end result of using low octane gas might be poor performance and a loss of power. On the other end of the scale the result can be melted pistons and destroyed cylinder walls. A lot of engines meet an early death from damage of this kind. In between the extremes are engines that cost a lot to repair.
To minimize the problem of old gas most engine manufacturers recommend that you buy gas from large brand name dealers. These gas suppliers normally have fresher fuel. Try to stay away from Ralph's Discount Gas Emporium type gas stations. It is also recommended that you be cautious of unknown marinas. Many boats have been run on marina supplied gas and have no fuel problems. A lot of fuel problems have been traced to marina gas. Bad gas can come from anyone's pump. When you find one or two suppliers with good gas, it is wise to stick with them.
Another recommendation is to buy enough gas for the day as opposed to buying gas for the next several trips. This is a good idea if you only use your boat once every month or two. You will need to know how much gas you will use for the days outing and you will want to take on extra gas for reserve. You can always get away with too much gas but you won't get home with too little. If you go home with fuel left over there will still be a stale fuel problem. With the lower amounts of fuel involved the problem is minimized.
If you use your boat regularly you probably fill the tanks for each trip. If you know the boat will not be sitting any length of time the best bet is to top off the tanks at the end of a days boating. This reduces the chance of condensation and water fouling the gas. Less air in the gas tank also slows fuel deterioration. An extra perk is that you will not have to fuel up the next time you head to the launch.
You will need to check with you owner's manual or your boat dealer as to the grade of gas you need to use. For the past several years it was recommended that you use premium grade for everything. The reasoning was that premium had more detergents than other grades and kept engines cleaner. This is no longer true. All grades have the same detergent package from any one manufacturer.
Recently I heard that it is a good idea to use premium because it has a longer shelf life. A few weeks after this another authority stated that premium gas has a shorter shelf life than the other grades as the boosters used in premium are less stable. The world of gasoline is still a confusing one and probably will be for some time. To keep the problems away be sure to buy a good quality gas and don't let it go stale. When you do fuel up, add a fuel stabilizer made for marine engines. You can get this product at you boating dealer. The price is minimal and it will protect the shelf life of the gas. It also traps the moisture in the fuel.
Another recommendation is to install a water separating filter in the fuel system. The first time it saves you from paying for a carb cleaning it has paid for itself two to three times over. They are easy to install and can be added to most any fuel system. Make a filter one of the first additions to your boat.
Gasohol is gas that has been mixed with up to ten percent grain alcohol This was popular in certain areas a few years back. I haven't heard of it's use recently but it still may be available.
Pound for pound, gasohol has less power than straight gas. Since marine engines are usually operated with the throttle in the wide open position the lower power factor has a great effect. The worse case effect is a destroyed engine. If for some reason you use only gasohol you need to have your engine modified for gasohol use. Contact you dealer for details. You can also expect slightly lowered performance.
Another problem with gasohol is a situation called phase separation. If enough water gets into the gasohol (about an ounce of water per gallon of fuel) problems arise. The alcohol separates from the gas and combines with the water. The alcohol/water combination drops to the bottom of the tank and is first in line to be taken into the engine. Your engine will not run on this combination. If you do get the system cleaned out what you will have left is very low grade fuel as the alcohol is also used to boost the gas.
Many marine engine manufacturers recommend that you avoid gasohol if you have the choice. If you do use gasohol be sure that it contains no more than 10% ethanol.
Carbon is a subject that is related to gas since carbon is a by-product of the combustion of gas. Carboning is one of the leading causes of poor performance and an early death in today's engines. This is more true with outboard engines than inboards but both are affected. Needless to say, how to prevent carbon build-up is something every boater needs to know.
Current gas formulas are good for the environment. They do reduce pollution. Sadly they are not so kind to engines as gas today tends to burn a bit dirtier than it did in the past. Carboning is a bigger problem than it once was. The addition of detergents had bettered the situation but in the case of marine engines it is not quite enough. We need to help things along.
There are two products that keep carbon buildup to a minimum. The first is an internal cleaning product that is injected into the engine while it is running. Then the engine is turned off and allowed to sit for a few hours before restarting. This will loosen and remove carbon from the engine. Once the engine is cleaned a carbon preventative can be used. This is a product that is added to the gas. Basically it is a detergent additive which enhances gasoline's cleaning abilities. You can get these products at your boating dealer and instructions for their use are printed on the containers. This two pronged attack on carbon will help keep an engine at peak performance and will greatly extend engine life. Product cost is more than made up from money saved in engine repairs and replacement. If you have an outboard and are using a TCW-3 oil then you already have the benefit of a detergent additive.
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