Outboard vs Inboard: How Do You Choose?

March 5, 2015 - 8:53 AM by Samantha Pudney

recreational boat with inboard/outboard motor

When choosing to buy the right boat, you’ve probably noticed three different types of engines: the outboard, inboard and inboard/outboard (I/O). You may already have set notions about one or the other, but the fact is that one is not really better than the other. It’s all a matter of preference and what you plan to do on and with your boat.

Before you make a decision, you should really assess what your plans are for your boat and how much you know about either engine. Then read on and find out which engine is best suited for you and your needs.

Inboard is in

An inboard will use a separate rudder to enable the boater to steer. These types of motors are popular with slalom skiers as they produce a smaller wake as well as fishing boats in heavy seas because they have a low center of gravity. If a heavier vessel chooses an inboard, they will need a motor larger in size and weight, which will not be appropriate for mounting at the aft end of the hull.

inboard motor

There are a few major drawbacks with inboards, but many boat owners overlook key features. Though inboard motors require a large box in the middle of the boat, which will keep the engine, they are much quieter than outboards, which is great for entertaining. They are more expensive than an outboard motor and harder to load onto a trailer, but because they were modeled after car engines, they are more fuel-efficient, have better horsepower and more torque. Because the transmissions are inside the vessel, more cabin space is allotted.

Inboards do, unfortunately, pose a potential fire hazard. Boats have been set aflame, but by running a bilge blower, you shouldn’t have a problem. With these motors, the benefits far outweigh the cons.

Outboards at a Glance

You’ve probably seen outboards on the boats of friends and family. They are popular among boaties and are often the default choice for both fishing and recreational and light commercial inshore boats.

outboard-motor

Many boaties find the easily-accessed mounting position of the outboard appealing because it allows them to lift the engine completely out of the water while it’s not in use. This is extremely beneficial for storage in the winter or even at the docks. This way your engine will not be sitting idly in the water where water inhabitants can attach themselves to the propellers.

If you choose to replace the motor later for a larger, upgraded model, changing the outboard engine is a cinch. It’s also much easier to service an outboard motor, and they have a good reputation with boaters for being reliable.

One of the biggest drawbacks, however, is that in order to get the power that the I/O has might take several outboards. If that’s the case, a boat is going to need a thicker, healthier transom. This will naturally make the boat heavier, requiring more fuel to power it. The outboard also takes up quite a bit of space so if you plan on entertaining more than two or three guests, you might run out of space.

In the Know with Inboard/Outboards

You may not know you’re looking at it, but the inboard outboard (I/O) is in the same general area as the outboard, though it’s usually tucked under a swim platform. This hybrid model is usually mounted at mid ship that drives a propeller shaft that passes through the bottom of the hull.

Power System Differences

Inboards and outboards have different powering systems, which will affect how you will be able to control your vessel at lower speeds. The outboard has the advantage because the integral skeg and directional thrust lets you manoeuvre easily without power. Inboards are difficult to steer unless you are applying the thrust. This can also make docking difficult.

Some I/O systems are equipped with a joystick control, which can simplify docking, but not all models have this feature and the ones that do can be pricy. Some joysticks are available on inboard models as well. What makes the I/O a nice hybrid is that it uses a similar steering system when the power is not on. This is because the outdrive is based off the lower unit of the outboard.

harbor-boats

Maintaining the Engines

Outboard motors are often preferred because you can work on it from inside the boat regardless if you’re in the water or not. The engine housing fully seals the engine and protects it from the environment while providing the ideal environment for the electronics and mechanics inside the motor.

The I/O motors and inboard motors share similar problems. The I/O is in a less ideal position because it is at the bilge of the boat where it can be damaged by water and moisture vapor. You won’t always be able to full access to the I/O, except through a small hatch. Inboard motors are in the same place as the I/O.

Because I/Os and outboards are in the water, there are possibilities of damage that don’t occur with inboard motors. Outboard engines are do not come with a drain for the winter. There is usually no need for this because the water drains when the engine is removed from the water.

Overall, I/Os are cheaper to replace if something goes wrong and need less maintenance attention than outboards. Most outboard motors will last for about 750 hours before they need serious repairs and maintenance attention while inboards and I/Os are good for 1,500 hours if they’re petrol engines, up to 3,000 if they’re diesel. Outdrives in I/Os will last for approximately 1,500 hours, and transmissions in inboards will last for about 3,000 hours before they need attention or replacements.

So Which to Choose?

That will depend on how you answered the questions at the beginning of the article. If you plan on inviting families and friends out on your boat, you might need more space than an outboard motor will allow, so opt for an inboard. Fishers might find an outboard motor to be the better option because the motor is easy to lift out of the water, allowing you to fish in a shallow area without getting the boat stuck. All in all, it comes down to your preferences and your needs.