Buying a boat and not sure what engine or drive type is right for you? We’ll run you through frequently asked questions to help you make the right choice and some common maintenance questions to make sure your boat engine will last.
- How Do I Choose the Right Boat Engine Type?
- Types of Boat Engines
- What is the Difference Between and Inboard and an Outboard Motor?
- How Often Should a Boat Engine Be Serviced?
- What Are the Signs of a Failing Boat Engine?
- How Can I Improve the Fuel Efficiency of my Boat Engine?
- What is the Best Boat Motor Brand?
How Do I Choose the Right Boat Engine Type?
The right boat engine type for you depends on how you'll use your boat. We'll walk you through 4 common engine and drive types to help you make the right choice when buying a new boat.
Types of Boat Engines
Diesel vs. Gasoline
Smaller inboards and outboards are almost all gasoline powered, but some larger recreational boats, many fishing boats and almost all sailboats are powered by diesel engines. While diesel engines are generally more efficient than gas engines, diesel also generally costs more than gasoline at the pump. Keep these tradeoffs in mind if you're considering two similar boats with different fuel types and choose the boat that will fit your needs and your budget best.
Outboard Engines
Small outboard motors like this one from Mercury are very popular on dinghies and other small boats.
Outboard engines come in a wide range of HP ratings and mount to the transom of a boat outside of the boat’s hull. These engines are found on a variety of boats from small runabouts to dual motor center console fishing boats. An outboard engine both powers and steers the boat using a tiller on smaller engines or the steering system on larger boats to turn the entire motor and change the direction of the boat. 4-stroke outboards are most common, but big manufacturers like Mercury and Torqeedo offer electric outboards as well for clean, almost silent power.
Inboard Engines
Inboard engines are usually 4-stroke automotive engines that have been modified to be used in a boat. The engine is mounted in the hull forward of the stern of the boat and is connected to a shaft that drives the propeller. On fully inboard boats, the propeller is also underneath the boat rather than protruding from the transom and does not turn to steer the boat. Instead, a rudder mounted to the transom of the boat is controlled by the steering system to change the direction of the boat. Inboard engines are popular on water sports focused boats as the propeller being under the boat produces a clean wake and there is no chance of the rider colliding with a prop at the back of the boat. Diesel inboards are also commonly used on sailboats as a way to motor in and out of the harbor.
Stern Drive Engines
Stern drives are often referred to as inboard-outboards as the motor is still mounted in the hull ahead of the stern, but the drive unit/propeller is mounted to the transom of the boat. The steering system of these boat engine types, like the steering system on outboards, turns the drive unit to change the direction of the boat rather than turning a rudder like an inboard engine.
Jet Drive Engines
Jet drives often have a large automotive engine as the powerhouse as well but suck in water through intake ports in the bottom of the boat and propel it out a jet drive unit mounted through the transom to propel the boat. Some boaters prefer jet drives since there is no spinning propeller that can potentially cause injury to swimmers in the water. Jet drive boats steer by changing the direction of the water stream as it leaves the jet unit.
What is the Difference Between an Inboard and an Outboard Motor?
The main difference is that an outboard motor is mounted on the transom of the boat and is a single unit containing the engine and prop. Inboards and inboard-outboards feature an engine mounted in the hull forward of the stern of the boat (usually an autmotive engine modified for use in a boat) and output to a drive and propeller either mounted underneath the boat or to the transom. Since outboards are outside of the boat, they are generally easy to service compared to inboard engines that are located inside an engine hatch and can mean some pretty cramped spaces when it's time to make a repair.
How Often Should a Boat Engine Be Serviced?
Servicing your engine yourself? We have all the boat engine systems products you need.
A boat engine should be serviced every 100 hours of use or annually, whichever comes first. Service generally includes changing the engine oil and oil filter on a four-stroke motor, changing gearcase lube in sterndrive and outboard engine, inspecting and replacing andodes, checking hyrdraulic fluid and installing new spark plugs if needed.
What Are the Signs of a Failing Boat Engine?
- Decreased engine power: A sputtering or surging engine is a bad sign and is often a problem with the fuel system or dirty spark plugs. We reccommend keeping a spare in-line fuel filter on hand so you can quickly swap it out and make it home if the filter gets clogged. NOTE: If you remove or work on any fuel lines, make sure to thouroughly vent the engine box to make sure there are no trapped fuel vapors before you start the engine.
- Strange engine noises: If your motor doesn't sound like it usually does, pay attention to it. Ticks, knocks or any other unusual noise could mean serious trouble and are worth investigating further. It could be as simple as low or contaminated oil or that your engine is about to throw a rod causing significant damage in the process. If you don't feel comfortable tracking down the problem yourself, take it to a professional boat mechanic. Need help finding a reputable mechanic in your area? Try out our Find a Pro tool.
- Engine overheating: If your temperature gauge is rising, your engine is likely not getting enough water. Check the raw water intake to make sure it isn't clogged. If that isn't the problem, check your raw water impeller. If the blade of the impeller are stiff, cracked or broken off, swap it out and check if your overheating problem is fixed.
- Engine wont start: If you turn the key and hear nothing or that tell tale "click, click click" of a dead battery, then the electrical system is probably the problem. Not sure if your battery is the cuplrit? We'll test it for free in any of our stores! Check out our In-Store Battery Testing West Advisor for more information.
How Can I Improve the Fuel Efficiency of my Boat Engine?
- Reduce drag and wind resistance: Lower your bimini top and keep the deck clear while you're moving. Adjust your trim tabs so that your boat rides better on the water or considering installing trim tabs if your boat doesn't already have them
- Reduce weight: If there is gear you are sure you won't need for this trip, leave it at home. NOTE: You should never remove safety gear from your boat to try to save weight. It's worth its weight in gold in an emergency.
- Keep your hull clean: If you store your boat in the water, make sure your hull is free of marine growth. A yearly coating of antifouling paint helps with reducing growth and helps protect your hull from blistering as well.
- Follow maintenance schedules: A well-maintained and well-tuned engine will run better and more efficiently and will also extend the life of your motor. Win-win.
- Maintain planing speed: Your boat moves through the water easier on a plane so trying to operate at this speed as much as possible will avoid expending more fuel to push through the drag at lower speeds. Adjusting trim tabs can also help your boat reach planing easier.
- Install a fuel flow sensor: A flow sensor tells you in real time exactly how much fuel your engine is consuming. This information allows you to accurately adjust both throttles and trim for maximum economy even as wind and sea conditions change.
What is the Best Boat Motor Brand?
It really depends on your preference and what type of engine type you end up going with. We carry Mercury outboards which have long been a staple of the boating industry and, in fact, the author of this article grew up water skiing and wakeboarding behind a 17' V-hull with a Mercury outboard that ran like a champ. If you're looking at an inboard power boat or a sailboat, odds are it will already have an engine installed unless you're buying a shell for a project. Swapping a motor isn't easy and you're better off taking care of the engine your boat came with and extending it's life as long as possible rather than trying to swap in a new one.
Now that you’ve got a primer, it’s time to start combing boat listings and dreaming of all the adventures you’ll have on your new boat. We’ll see you on the water!
Need Engine Parts?
West Marine offers a complete selection of Sierra aftermarket replacement parts for most makes and models of outboard motors, stern drives and inboard engines. To find the part(s) you need, use the Sierra Online Applicaton Resource, referred to as SONAR for short.
Need More Help?
Your local West Marine is full of life-long boaters. Whether you need help tackling a DIY project or are stocking up on safety gear for an offshore trip, we have the gear and know-how you need. Find your store here.
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