IPS vs Shaft: The Truth About Pod Drives

We’ve all heard the horror stories – but how good, or bad, can they be? Pod drives, such as Zeus or Volvo IPS (Inboard Propulsion System) are all so popular in Australia. There are many boat manufacturers that come to mind who are using them, fitting up to 3 in a boat.

A gearbox and drive system that is mounted beneath the boat is called a POD drive. These steer on a large axis. When mounted in twin and triple set-ups can be used with a joystick for ease of parking. Much like a sterndrive, the drive is incorporated with the exhaust and water inlet. They are mounted in a manner that allows them to increase fuel efficiency, and reduce drag.

What are the differences between IPS and Shaft?

There are two main brands in the market – Volvo IPS and MerCruiser Zeus. There are some distinct differences – such as:

A shaft drive is traditionally a shaft with a propeller, and a rudder mounted behind for steering. You must understand the principles of driving a shaft, before operating as there usually isn’t a joystick. Although, manufacturers are starting to combine bow & stern thrusters with a joystick set-up. A shaft drive will usually have lower fuel efficiency over a pod. However maintenance is decreased because there are less moving parts, and less parts mounted underwater. Typically pod drive oil is expensive and needs to be changed regularly. Seals in the gearbox that stop water from entering can wear out. Therefore you must keep a close eye on the gearbox at each service interval to ensure they stay water free. Each metal pod requires special anodes designed to sacrifice first, which protects it from eroding away.

The last thing to consider is availability of parts and technicians to work on them. If you’re planning some serious offshore trips, and extended trips to remote locations, you need to consider the serviceability implications. With that being said, you will definitely save fuel on longer trips, and achieve more distance between refuelling. POD drives also tend to be smoother and quieter, although there are a number of different factors that can affect this.

What to look for when buying an IPS or Zeus pod?

Pre 2009 IPS drives were fitted with certain parts that are now superseded, one being a bronze steering seal. When used in salt water they were prone to failing sooner than expected. Although Volvo never actually did a recall, they are now fitting a stainless steel version. To replace the ring is a labour intensive job. This includes the removal of the drive and top box – the cost of the part itself is around $1000. For a Pod that is more than 5 years old, it is a good idea to replace the seals, and keep a very close eye on water levels. If water starts to get in, it will then cause damage to the clutch plates in the gearbox. This becomes a spiralling effect, and before you know it you’ve spent upwards of 15K rebuilding a single gearbox.

How will I know there is water in my gearbox?

Fortunately we’re no longer in the Stone Age – we can use oil sampling to check for water mixed with oil. Anyone buying a pod out of warranty should consider testing a sample to see if the seals are leaking salt-water in. If you already own the boat you can monitor it at each service, or more regularly if you’re concerned.

What to look for when buying shafts?

Fortunately shafts have been around for a long time, and there are more mechanics competent at checking them. The 4 main things to look for when buying a shaft are checking its condition (straight etc.), the skeg bearing, the alignment, and the propellor. Generally speaking, the worst case repair for a small shaft and propellor would be in the vicinity of $2000-8000, whereas for a POD you’re looking at upward of $20000 just for the drive.

So, what’s best – IPS or Shaft?

It really comes down to the purchaser, how they’re planning to use the boat, and budget. For lots of driving to remote locations – shaft all the way. When it comes to larger boats (60ft plus) – shafts again. For anything else in between e.g. parking at marinas, coastal hopping and inshore cruising – Pods are a great option. Another advantage of pods is that the cabin set-up can be completely different, proving better layouts. Pod engines don’t have to be mounted in the middle of the boat. As long as you’re aware of the additional cost from the beginning – pods can be great. Technology and complex machinery costs money, and you’re going to pay more to maintain pods if you keep the boat long-term.

If you ask someone who has owned a shaft their whole life, they probably aren’t going to be a fan of the IPS. Those who have owned them and couldn’t afford to maintain them will have mixed emotions. A well maintained pod is a great advancement in technology, and many who finally come around to owning them end up enjoying really enjoying the benefits they have to offer.

If you are still tossing up on which drive type is right for you, read How to Choose A Boat – 4 Major Drive Types Explained.

What is a pod drive?

Pod drive is a marine propulsion system where the gearbox and drive is mounted right beneath the boat in the water. They steer on a large axis, and when mounted in twin and triple set-ups can be used with a joystick for ease of parking. Much like a sterndrive, the exhaust and water inlet is incorporated with the drive and they are mounted in a manner that allows them to increase fuel efficiency, and reduce drag.