What does the outdrive connect to?

For years there have been debates about whether sterndrives or inboards are better. In this post, we’ll present the facts and let you decide on the rest. Both have pros and cons and are two completely different machines.

First of all, let’s start by explaining what exactly sterndrives and inboards are.

A sterndrive is a marine propulsion system that is attached to a sterndrive, also known as an outdrive. The drive unit is both the transmission and propulsion. When the captain turns the steering wheel, the entire drive turns. No rudder is needed.

An inboard is a marine propulsion system that is enclosed within the hull of the boat — it is usually connected to a propulsion screw by a driveshaft. The driveshaft goes from the transmission to a propeller outside of the boat. The boat is steered with a rudder when the steering wheel is turned by the captain. The propeller then pushes the water past the turned rudder and turns the boat.

Now let’s look at the pros and cons of both.

• Sterndrive’s provide the boater with a versatile range of trim. This allows you to raise the sterndrive up when loading/unloading or when in shallow water. It also allows smoother rides when trimmed up. Trimming down allows quicker acceleration.  However, inboards draw less than a sterndrive does if the sterndrive is all the way down (inboards need less water to float). Sterndrives draw less when slightly tilted up.
• Sterndrives will go faster than an inboard with the same horsepower and even use less fuel. On the other hand, inboards will hold a speed more easily than a sterndrive.
• Sterndrive’s put out great wakes for wakeboarding; inboards create flat wakes for waterskiing.
• Inboard boats go in one direction in reverse no matter what the position of the wheel. With a sterndrive boat, reverse thrust is directional.
• Sterndrive’s can, at times, have higher maintenance requirements than inboards. However sterndrive motors are easier to get to.
• Inboard propellers are tucked up underneath the boat, which can be much safer than a sterndrive tilted up; but without a tilt up mechanism, an inboard engine has a larger draft.
• Since a sterndrive boat has the equipment on the back of the boat, it allows more room onboard than an inboard boat.
• While sterndrive boats allow a smooth ride when trimmed up, larger boats with inboard engines can have a smooth and stable ride as well. Since the motor is deep in the hull of the boat, it improves stability because it lowers the boat’s center of gravity.

These are just a few examples, and as you can tell, there are plenty of pros and cons to each propulsion system. Depending on your budget and how you’re going to use your boat, either of these will get the job done and give you an enjoyable time on the water. Still have questions? Contact our sales team and we’ll get you going in the right direction.

Last Update: May 30, 2022

This is a question our experts keep getting from time to time. Now, we have got the complete detailed explanation and answer for everyone, who is interested!

The drive unit (outdrive) carries power from the inboard engine, typically mounted above the waterline, outboard through the transom and downward to the propeller below the waterline. ... The boat is steered by pivoting the outdrive, as on an outboard motor; no rudder is needed.

How does an outdrive connect to the engine?

ANSWER: The engine coupler connects the engine to the outdrive, which is outside of the boat. The coupler is made of aluminum and rubber, which isolates the vibration between the engine and the outdrive.

How does a stern drive engine work?

A stern-drive engine is attached through the transom to a drive unit (also called an "outdrive") that is essentially the lower unit of an outboard. The engine turns a drive shaft that is attached to a propeller at the other end.

How do you know your outdrive is bad?

Bad outboard lower units can give the operator shifting issues, and other signs will include water in the gear lube, metallic particles on the drain screw magnet, clunking sounds when shifted, or the loss of the ability to shift into gears.

Can you fill lower unit oil from top?

Filling from the top down will not allow all the air to escape from the gear box ... The heavy gear lube will stop flowing down as cohesion from surfaces slow it down till it stops as the air wants to go out the top hole ... If you let it sit overnight all the trapped air would eventually make its way up to the top ...

43 related questions found

Most boats must be in neutral before starting the engine. If your boat is in gear, the engine will not start, but other components like the lights and gauges will work.

Not many people talk about that, but it just shows the technology in the sterndrive market.” Technology has also improved corrosion protection – especially in the saltwater environment – for sterndrives. ... So you can have a successful sterndrive experience in saltwater.” All of those things sound good.

It's also common to expect between 10-15 years out of a well-used sterndrive and transom assembly, and then it's a matter of continual repairs or replacing it once and for all.

Inboard boats, including direct drives and V-drives, are the only types of boats you can safely wakesurf behind. ... To recap, you should ONLY wakesurf behind an inboard board, never behind an outboard or inboard/outboard (stern drive) due to the risk of making contact with the propeller and the proximity of the exhaust.

No it shouldn't be able to spin freely when it's in gear. When u put it in forward and u turn it u should have to really pull on it to get it to go around.

A V-drive is more efficient in delivering horsepower to the prop, losing only 8 percent, while a sterndrive loses 13 percent. Yet, all other things being equal, a sterndrive is faster and more fuel-efficient.

If you want a transom for water play, the smart move is to get the sterndrive. If you want better corrosion resistance and easier maintenance, plus drives that can be trimmed clear of the water, go for the outboards. It's your call, and with the Aviara AV32, either choice is a winner.

(Entry 1 of 3) 1 : inside the line of a ship's bulwarks or hull. 2 : toward the center line of a vehicle or craft (such as a ship or aircraft) inboard.

A V-drive and a direct drive are both inboard propulsion systems, which means the engine drives a propshaft that passes through the boat bottom, with the propeller positioned under the boat and steering accomplished by a rudder.

A stern-drive engine is attached through the transom to a drive unit (also called an “outdrive”) that is essentially the lower unit of an outboard. ... Steering of stern-drive boats is controlled by the outdrive, which swivels like an outboard engine to direct propeller thrust.

And finally, when it comes to storing your sterndrive, it's important to prevent water from entering the exhaust hub of the propeller. Openings that are designed to let the exhaust out can also allow rainwater and snowmelt in. Water will accumulate in the unit's housing if the drive is stored in the "up" position.

Are sterndrives reliable? Yes, provided correct maintenance procedures have been carried out at the required intervals. Sterndrives on trailer boat applications are more reliable than permanently moored sterndrives.

Outboard engine boats are better suited for shallow water, salt water, and pontoon boats.

Not only is saltwater harder on you, but it's also harder on your custom powerboat. Saltwater is around five times more corrosive than freshwater, and the salty ocean air corrodes metal ten times faster than inland air.

While it won't really hurt the engine, it isn't a good idea IMHO, since you could get injured by it. You're much better off starting any boat with the transmission in NEUTRAL.

So the answer to the question is, no, a typical boat won't start when it's in gear. The engine may crank and the lights may turn on and off, but that will be it. Shift the lever to bring it to neutral and voila, the boat should start up easily again.

If it is in the 'off' position, your boat will not start no matter what you do. Make sure that your boat is in neutral. Generally, this will be with the shift lever in the up position, or the middle position between reverse and forward.

One of the most common questions I get asked when someone is choosing a boat is “Should I buy this boat for X amount?” Before I can give a good answer some basic details need to be figured out. First, you need to determine the main purpose of your boat (for example: fishing, cruising, watersports etc). Second, where you’re going to keep it. Are you going to moor it, or trailer it? Of course, the size of the boat may dictate this, but not always. Where you’re planning to store it may also affect the type of engine setup that you choose and vice versa. How do you know what type of engine and drive you should get?

Here’s a rundown of your options on how to choose a boat to help you figure out whether to moor or trailer, and what sort of engine and drive to go for.

How to Choose a Boat – Moored or Trailered?

When choosing your first boat you need to think about how you will get to it, and how to get your boat in the water.

• Do you have a big enough car to tow it?
• Will you have a berth or a mooring?
• If you have a mooring, how will you get out to the boat?
• Will you use the boat regularly enough to keep batteries charged?
• If you have a waterfront property with a slipway, is it set up to accommodate your choice of boat and if not, what else needs to be done?

Maintenance costs vary greatly depending on whether the boat is kept permanently in the water or not.

Moored Boats

When you have a moored boat, you will need to have it slipped, cleaned and antifouled every 6-12 months. The reason for this is that over time the part of the boat in contact with water will accumulate barnacles and moss. Antifouling reduces the amount of growth and it also becomes easier to clean off when you have a protective coating. You will also need to change corrosive anodes to stop metal parts (e.g. stern drives, shafts, propellers etc.) of your boat corroding away.

Trailer Boat

When you store your boat on either a trailer or dry-dock, you no longer need to antifoul the boat as it isn’t in contact with the water. This will minimize maintenance costs, but you will still need to consider:

• Storage – garage, warehouse, off-street or on-street?
• A suitable car to tow – for instance, once a boat and trailer combo weighs over 2 tonne you’ll need to carefully consider your tow vehicle.

How to Choose a Boat: Engine and Drive Setup

How a boat is powered and the type of transmission attached can also have a large impact on maintenance costs. Let’s look at the different drive types, and review the pros and cons of each.

There are four major drive types you will come across when buying a boat:

1. Inboard Stern drive,
2. Inboard Shaft drive, and
3. Outboard
4. Pod Drive

There are other setups available but these are less common in Australia.

Inboard Stern drive

Stern drive is a transmission and engine package, which combines outboard drive with an inboard engine. They come in all different combinations: large stern drives coupled with diesel engines or smaller ones coupled to petrol engines. They are also available from a number of manufacturers but the two most common brands in Australia, for example are Mercury and Volvo.

Example of a Volvo Penta Diesel & Stern drive setup

Inboard Shaft Drive

A boat with a shaft drive has the engine mounted inboard, with a shaft through the hull driving a propeller. Shaft drives may have the engine mounted in a few different positions, including (but not limited to) middle and rear. A rudder behind the propeller steers the vessel.

Transparent view showing a mid-mount shaft drive

Outboard

Outboards have the engine attached to the stern, on the outside of the boat. It is a single unit, which includes the engine and transmission in the one package.

Yamaha 80hp Four-Stroke Outboard

Pod Drives

Vessels fitted with pod drives have the engine mounted either in the mid or the rear of the boat, with a “pod” incorporating the transmission, propellers and outdrive straight through the bottom. A pod can steer left to right, and the two most popular brands are Volvo IPS and Cummins/Mercruiser Zeus drive.

How to Choose a Boat: Advantages and Disadvantages

Stern drives

When you choose to buy a boat, there are several options to consider. Typically the main reason people buy second hand boats fitted with stern drives is because they are common, cheaper than other types and provide good handling characteristics. They allow you to trim up and down to shift the planing position, and the whole stern drive physically moves when you steer. Stern drives are a great option for a trailer boat, especially as you won’t have any barnacle growth on them. They need to be serviced yearly, but are a good all round option.

When a stern drive is used on a moored boat it becomes the less desirable option. Stern drives usually have rubber bellows that house drive components and stop water entry. These crack with age, and if you leave your boat moored over time it will grow barnacles. When the leg is turned to steer the sharp barnacles can pierce the bellows, allowing water entry. The water can then cause damage to bearings and other components and if left unattended it may even cause the boat to sink.

Another thing to be aware of is the water pickups, which cool the engine. These are mounted on the stern drive from factory. In the picture below they are covered in barnacle growth, which would cause the engine to overheat under load.

Example of Mercury stern drive with growth from sitting in water for a long period

Shaft drives

Shaft drives are a much better option if you’re intending to moor the boat. Barnacles will still grow on them but there is no rubber bellows to change, as they don’t have to steer. They have shaft seals that can wear and leak over time, but don’t cost as much to maintain.

A downfall of a shaft drive is that they draw more water, so you cannot enter shallow waterways. They do need anodes fitted yearly, but so does a stern drive. As for handling, a single engine shaft drive can be more difficult to steer compared to a single engine stern drive. If you have twin engines, then shaft drives are an easier boat to manoeuvre. Twin shafts allow you to split the controls, using one engine in forward and one in reverse, spinning the boat on the spot – this works too on a stern drive but to a lesser effect.

Outboard

Outboard powered boats can sometimes have the best of both worlds with regards to maintenance costs. They are easily removed/replaced if a major repair needs to take place, and can be trimmed upwards to keep them out of the water, hence not needing to be antifouled. Outboard boats also provide the handling benefits of a stern drive, in that they can be trimmed up and down and steer left and right. They offer more useable boat space, because the motor isn’t mounted inside.

The disadvantages of outboards are when you need certain weight distribution, bigger horsepower, or diesel power. Some people prefer shaft drive or inboard for fishing, so they can fish off the back too.

Pod drives

Pod drives are exclusively paired with diesel engines, and provide a number of benefits. All pod drives are coupled to a joystick, which enables control of the boat without manually engaging gears and steering. This makes the learning curve for docking the boat much easier. Pod drives are also between 10-30% more fuel efficient than a traditional shaft drive, as they can propel the vessel with less drag. Zeus pod drives offer inbuilt trim tabs and have rear facing propellers, where as Volvo IPS do not offer trim tabs and have forward facing propellers.

The disadvantages of pod drives are that they cost more than a regular shaft drive to maintain. They do not have rubber bellows like a traditional sterndrive, but use expensive synthetic oils that need to be changed regularly, along with anodes. Pod drives are very sensitive to water entry, and certified technicians are required to work on them. This means there are less people available to fix them should you have issues in remote locations.

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