Choosing Boat Motors for More than Personal Reasons.       CLICK HERE FOR GREAT BOATS

Personal feelings aside, choosing a  motor requires more than just the cost.  The boat you choose and how you plan to use it needs to be determined, first. Diesels boat motors offer outstanding durability under frequent use. In fact, many mechanics suggest that the primary reason for diesel engine problems is lack of use. A diesel that sits idle for weeks at a time can form rust on its cylinder walls, causing loss of compression, making it difficult to ignite the fuel. The fuel itself can even begin to grow microorganisms. Diesel boat motors that never work harder than running at harbor speeds often "coke up," meaning they build up carbon in the cylinders. That leads to problems — and expensive repairs.  

If you plan to use your boat often, spending the extra money on a diesel power would be very cost-effective in the long run. A heavy boat demands a lot of muscle to push it through the water and it’s not unusual for  diesel boat motors on a commercial vessel to go 10,000 hours between major overhauls. A properly maintained diesel engine that works hard daily can outlast several gasoline motors of similar size. 

Making a direct comparison between gasoline and diesel boat motors is not going to give you the answer you want because they are measured differently. The horsepower of a gasoline engine is rated at or near wide-open throttle, which may be at 4,500 rpm or more. Diesel engines are rated at continuous duty, typically in the 2,000-to 2,200-rpm range. The actual horsepower of any engine drops quickly as the rpm drops. 

Today's diesels are lightweight, smooth-running boat motors, but they are still expensive, often costing twice as much as a gasoline engine of similar output. Cost is the primary reason why so few powerboats are equipped with diesel 

The gas engine has the edge when it comes to quick bursts of speed from a boat motor. Gasoline engines offer maximum flexibility in drive configuration, and are cheaper than diesel motors. In addition to the superior bursts of speed and throttle response, they don't "mind" going unused for longer periods of time. On the plus side, gasoline is available just about everywhere, whereas sometimes diesel fuel can be hard to find. With few exceptions, true marine gasoline engines are not available to pleasure boats under fifty feet long.  Boat motors run by gasoline available are, in fact, all “marinized” versions originally developed for automobiles. Important changes are made to the bearings, lube oil system, cooling system and exhaust manifold when an automotive block is converted into a marine engine. 

Two most critical features to turn a land engine into a boat motor is a “wet” exhaust system and non-sparking electrical parts (required by U.S.Coast Guard Regulations). Both gasoline and diesel boat motors must have water-cooled exhaust manifolds to prevent red-hot iron from becoming a fire hazard. Cooling water is injected into the stream of hot exhaust gas through an elbow specifically designed to prevent water from being sucked back into the cylinders, routing the potentially legal gas through the rubber hose to an outlet fitting at the transom. Gasoline fumes are heavier than air. They collect in the bilge where a spark from a starter motor, alternator or distributor could ignite them. 

The major difference between gasoline and diesel boat motors is the way the fuel is ignited in the cylinder. Gasoline engines require a spark plug. Diesel engines use the heat created by compressing air in the cylinder to ignite an extremely fine spray of fuel. Spark ignition requires a volatile fuel, such as gasoline. Diesel fuel is less volatile. 

Do you want speed and quick turns?  Will you be out on the water every weekend? Knowing what you need before selecting your boat motor helps you make the right choice when talking with the dealers. With the increase in gasoline prices continuing to rise, the diesel boat motor doesn’t seem to cost as much as considering how long you plan on using your boat.