Outboards versus inboards

Thursday, 27 January 2022 11:50 am

What is the best choice?                        

With the new outboard technology we have access to now, many operators are contemplating whether to install outboard engines or stay with inboard diesel engines on their vessels. Outboards are getting larger so its becoming a tempting option! See attached photo below of a 17m recently launched here on the Gold Coast in Australia.

There are pros and cons to using both types of propulsion in your new vessel.

Outboard pros:

* No requirements to design engine rooms below deck.

* No requirements or large costs for parts and labour to fit out engine rooms with sea water inlets, stainless steel plumbing, fire suppression systems and fire rated insulations.

* Overall vessel build time is quicker.

* Outboards can be easier to service if vessel can be lifted easily.

* Outboards can be changed over quickly with less vessel downtime.

* Overall build cost can be lower using outboards.

Outboard cons:

* Engine longevity can be lower than inboard diesels, resulting in quicker change overs.

* Lower torque can result in slower response time to manoeuvre. 

* If using petrol outboards then petrol storage needs more attention in design and placement.

* Safety aspect of carrying petrol on board as opposed to lower flash point diesel.

* Electrical installation costs can be higher during build if using quad engines.

Inboard diesel pros:

* Usually a little more fuel efficient than outboards ( subject to vessel design and capacities)

* Usually longer overall engine life.

* Higher torque with bigger propellers for more response during manoeuvres.

* Can be serviced in situ while vessel is on water - no need for lift out.

* Diesel is safer to use than petrol.

* Overall through life vessel costs lower using diesel inboards.

* Ideal for larger capcity vessels.

Inboard diesel cons:

* Initial set up costs are more due to addition of propulsion package and engine rooms.

* Additional servicing and cleaning of engine rooms and fire suppression systems.

* Propulsion units will also require additional inspections and servicing.

* Longer labour time to change over engines, resulting in vessel non operational longer.

Inboard diesels may cost more up front, but if you intend holding your vessel long term, then your through life costs can be lower.

If a fast changeover of engines and cheaper upfront build cost is important, then outboards are a great option.

Diesel outboards are also a great option, although  horsepower availability is not currently as high as petrol outboards.

Latest 17m design below using 4 x 300hp Yamaha outboard engines and demonstrating that when combined with good design and hull efficiency, outboards are a good option. For more information please email us here: info@goldcoastships.com.au