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Inboard vs Outboard. Which is Better?

Well, here we are.  Winter has set in (at least for most of us). Our boating time has been severely limited or maybe even eliminated until spring.  What do we do?  We dream of summers gone by and summers to come.  We plan the boating projects for the season so our water rides will be ready to go for the next season.  We talk about boats and boating and pontificate on things such as which one is better, inboards or outboards.  This is a debate that has gone on for years and everyone seems to have their preference.  Let’s take a look.

For the purpose of this argument, let’s say that an outboard engine is one where the engine and transmission are outside the hull of the boat in its entirety and an inboard engine is one where the engine and transmission are inside the hull of the boat in its entirety.  Yes, I know that we also have sterndrives where the engine is inside the hull and the transmission is outside.  These designs were created to take advantage of some of the positive attributes of both inboards and outboards.  They are basically hybrids.  
Typical Outboard Engine Setup
Typical Inboard Engine Setup

Convenience of Use

Naturally, if the engine is inside the boat, it is taking up space in the boat.  This is where an outboard engine has an advantage.  By hanging the engine on the transom, there is more space in the boat for people, storage or whatever.  *Advantage Outboards

Then again, many boaters like to have a swim platform for swimming, fishing or just hanging out.  The ability to back into a slip and easily step on an off the boat without having to step over or around an engine is definitely a plus.  *Advantage Inboards


Most inboard engines are engines that were originally developed for motor vehicles and then converted for marine use so they could be used in boats.  If you are already used to working on your car, you may feel right at home working on an inboard boat engine.  They are also quite easy to work on provided that you have enough space in the bilge.  *Advantage Inboards

Outboard engines are a bit more convenient, especially for those that are not mechanically inclined.  You do not have to winterize them and everything is easy to get to on the engine.  Typically, basic tasks such as checking the oil are easily done. *Advantage Outboards

Engine access for outboards is typically quite easy.

Outboard engines are a bit different in their set up so if you are not used to working on them, there may be a bit of a learning curve but it is not a big one.  They are, however very easy to get to.  After all, they are not sitting down in a bilge like inboards are.  All that is typically needed is removal of the engine cover.  *Advantage Outboards

Because of their origination, Inboard engine parts are easily available and tend to cost less.   In some cases you can use the same parts that are used on motor vehicles**.  If you re good with tools and are comfortable working on engines, parts are typically easier to replace on Inboard engines.  Again, this does somewhat depend on the placement in the bilge.  *Advantage Inboards

Inboard engines are pretty easy to work on provided there is enough space in the bilge.

**It is important to never replace engine electrical components such as an alternator with parts designated for an automobile.  Installing electrical components not designed for marine use on an inboard engine could lead to conditions that could cause an explosion.


If you have an inboard gasoline engine, it is important to run your blower for at least 5 minutes before starting the engine.  This ensures that any gasoline fumes that may be in the bilge are expelled before the engine is running.  Your blower should also be run anytime the engine is at idle speed for an extended period of time.  Failure to do so could result in an explosion if there is a fuel leak anywhere in the system.  With an outboard engine, this is not an issue because the engine is not in an enclosed area.  *Advantage Outboards.

If part of your boating fun includes skiing, swimming or any other form of water sports, you probably are aware that keeping clear of your boat’s propeller is an important thing to remember.  On many occasions, I have seen people suffer cuts and bruises because they accidentally came into contact with a boat propeller or the lower unit.  The most recent I one I observed resulted in a young lady being taken to the hospital for stitches.  Just in case you are wondering, the propeller was not turning and the boat was not running.  Boats with inboard engines tend to have the propellers up under the hull as opposed to below the transom.  While it is not impossible to come into contact with it, it is much less likely.  *Advantage Inboards

 Engine Performance

Newer outboard engines have a lot of technology in them and that technology is allowing manufacturers to squeeze out more and more horsepower per cubic inch.  The days are gone when outboard engines maxed out at 200 horsepower.  Using today’s technology, there are several models that produce 350 horsepower or more and a few models that produce in excess of 500.  This can all be done with an engine that is still quiet and relatively fuel efficient when not pushing the throttle to the max.  *Advantage Outboards

Seven Marine is one manufacturer that excels at getting more ponies out of an outboard engine.

Don’t rule out the inboards yet when it comes to performance though.  People talk horsepower a lot but don’t forget about torque.  That is important, especially if you have a larger, heavier boat.  Inboard engines win the race here because their placement in the boat allows them to be bigger and beefier.  They can deliver higher torque than their smaller outboard counterparts and therefore can deliver more horsepower at lower RPM’s. In addition, if you need something that can pump out more than 500 horsepower, outboards start to fall behind.  Granted, you can put multiple outboard engines on the back of a boat but with a Yamaha 350 costing north of $25K and a 7 Marine 627 costing around $90K, that can make things get very expensive very quickly.  *Advantage Inboards


Over the years, marine engines have become more reliable overall, whether inboard or outboard.  The fact is, however, that both types will eventually wear out.  Unfortunately outboards tend to wear out more quickly than inboards do.  The reason for this is that outboard engines typically have to rev higher than inboards do in order to achieve the rated horsepower.  The more revs, the quicker it wears out.  My current boat has a pair of 454 cubic inch Crusader inboard engines.  They are currently 30 years old and still run like new.  While there are also some outboard engines out there with just as much (if not more) age on them as my engines, it is not as common.  Does this mean that I can expect my outboard to last only a few years if I use it regularly?  Of course not.  Any well cared for engine should give you many years of use before it is time to repower.  I would also say that outboard engines built today would probably last longer than one built 30 years ago.  *Advantage Inboards


Did you notice the prices that I mentioned for outboard engines in the Engine Performance section?  Outboard engines are not cheap!  They do cost significantly more than comparable inboards.  Again, the advantages of outboards may be worth it.  For example, swapping out an outboard engine is a lot easier than swapping an inboard.  Keep in mind that if you replace an outboard engine, you are replacing the lower unit as well.  That is the equivalent of your transmission.  With an inboard engine, the transmission is typically a separate component.  That being said, the cost of an outboard is still higher than the equivalent inboard setup.  *Advantage Inboard

Boat Handling

If you have ever tried to back a single engine inboard powered boat into a slip then you have experienced one of the reasons why some people like outboards.  Inboard powered boats use a rudder for steering and rudders require a certain amount of water flowing by it to work.  This means they don’t work well at slow speeds in reverse.  Outboard engines allow the thrust to be directed in the direction necessary to maneuver the boat which makes handling the boat, especially at lower speeds, easier.  Outboard engines can also be trimmed up to allow the boat to run in shallower water.  *Advantage Outboard


When it comes down to it, most people have a preference as to what they like.  Many boats come with one type or the other and that becomes the determining factor in whether you end up with an inboard or an outboard.  So, when you are looking for you next boat, or considering a repower, remember the advantages and differences when comparing the two.

Happy Boating

Captain Frank
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