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Comparisons of costs

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Upon a recent browse of some online naval architecture forums, several discussions related to surface drives repeated a common myth:

 

Surface drives are expensive

 

This belief is false.

Surface drives could, perhaps, be considered expensive when compared to conventional fixed pitched propeller systems. However, on a performance basis, a surface drive will always achieve higher speeds than conventional propellers. When compared to other types of propulsion, the surface drive is generally the least expensive option.

Cost comparisons, surface drives versus:

Outboards:

  1. With a few exceptions, outboard engines operate using gasoline, which is generally more expensive than diesel.
  2. The life cycle cost of outboard propulsion is very high. Over the long term, an outboard can cost the owner over 200% of its’ acquisition cost.
  3. On larger horsepower outboard engines, the acquisition costs, though they may be slightly cheaper than inboard / gearbox / surface drive packages, often show only modest price differences among major brands.
  4. Ease of maintainance and low cost of spares are the typical cost savings.

 

Stern Drives:

  1. Acquisition costs for major brands (Such as Mercury, Volvo, Konrad) can be as much as 50% to 100% higher than that of a surface drive.
  2. Stern drives are mechanically complex devices. The life cycle costs of a stern drive typically are two to three times the acquisition cost over the life of the drive. Seals and gaskets are notoriously prone to failure on these units.
  3. Stern drives are often priced “piecemeal”, with many “options” truly not optional.

 

Pod Drives:

Much is often trumpeted in the marine press about pod drives…

  1. They have a reputation for being expensive on acquisition (sometimes 200% or more over a surface drive)
  2. They are extremely complex in design, resulting in extremely high maintenance costs.
  3. They are not easily accessible for maintenance in most cases, leading to higher costs.
  4. Hull modifications are usually required.
  5. Because they extend below the hull, many are frequently damaged by hitting underwater objects, debris, etc.

 

Water Jets:

  1. Acquisition cost varies greatly. From about the same as surface drives on small jets to over twice the cost on large jets.
  2. Water jets are mechanically complex, leading to short life cycles and high maintenance costs.
  3. Water jets have an Achilles’ Heel with maintenance, and it is dirty water, shallow draft (sand intake), or debris in the water. These situations lead to very expensive repairs.

 

We have left out of this discussion more exotic high speed propulsion, such as some CPPs, SES, Foils, and systems intended purely for racing.

When looked at objectively, from a purely cost standpoint, surface drives are effectively, in most situations, the most cost effective propulsion except when compared against conventional shafts and propellers.

It is somewhat perplexing how surface drives came to be regarded as expensive. Some theories:

  1. Surface piercing propellers are usually more expensive than conventional propellers.
  2. Some surface drive systems on the market were designed primarily for racing. These systems are often not suitable for military, recreational, or commercial applications, and are often made on a custom basis. Many drives on the market were designed by former racers who, although they had racing experience, had little or no maritime or design experience. This situation is most often seen with fixed shaft surface drive models.
  3. With the exception of France Helices, Arneson, and ZF, the other surface drive manufacturers are small companies with minimal distribution chains and high operating costs.
  4. Many surface drives are often installed with mis-matched propellers. This is an enormous expense that gives surface drives a bad reputation. France Helices is the only surface drive manufacturer in the world that is also a propeller maker. This is also why we do not sell our drives without propellers (Though we will manufacture propellers for other brands of drives).

So, which type of propulsion is right for your application? There are more important things to consider other than pure costs. The next article will delve into these reasons.

 

 

 


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More Stories By John Miele

I am currently Sales and Marketing Manager, Asia / Pacific for France Helices. Created in 1977 by Paul BEZZI, FRANCE HELICES is today an international company. French marine propulsion leader, FRANCE HELICES is also one of the international leaders. Research and development are a very important part of FRANCE HELICES program, the CAD's department is equipped with the latest computer technology, using most up to date programs. Our engineers and technicians determine from the customers specifications and designs, the type of propulsion system to suit the boat's application. They can also advise on the ideal choice of power and optimum gearbox ratio to obtain the maximum thrust. There are many FRANCE HELICES' inovations and patents such as Surface Drive System (SDS) which enable boats to obtain very high speed with excellent handling capabilities and high quality Controllable Pitch Propeller systems (CPP) for both professional use and pleasure application. The constant research using cavitation tunnel testing, guarantees high efficient propeller blade shape for our customers. More than 20 000 propellers per year are manufactured by FRANCE HELICES workshops. In all sizes from small sailing boats to large fishing vessels to navy boats or mega yachts. The FRANCE HELICES workshops are equipped with modern foundries capable of casting propellers up to 3.5 tons in NiBrAl. They are also equipped with CNC milling machines and CNC lathe machines. FRANCE HELICES has four sites which cover the complete range of production. The development of FRANCE HELICES, supported by shareholders places our company as a leader in the international market and insures a constant development, worldwide, in order to be close to the end user.

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