Fitting the square peg into the round hole

Marinediesel engines are compact. How compact?

Well, our VGT Series of engines are take up a mere 0.625 cubic meters of space.

Compare this to our competition (taken from the product data sheets produced by the manufacturers):

Yanmar 6LY3 – 0.926 cubic meters

Cummins QSB 5.9 – 0.762 cubic meters

Cummins QSB 6.7 – 0.856 cubic meters

Volvo D6 – 0.699 cubic meters

FPT N60 – 0.896 cubic meters

With an engine as compact as the VGT Series, and as flexible with remote component location (like the intercooler or starter), the VGT Series will fit into cramped engine compartments, such as those found on RHIBs or small patrol boats.

Additionally, smaller size translates into a much lighter engine, a critical feature when discussing vessels that will exceed 40, 50, 60, or even 70 knots in speed.

With this size and space differential, using one of our competitors’ larger engines truly is a case of trying to fit the square peg into the round hole.

Why waste money on an outboard? The Marinediesel VGT Series makes them obsolete!

Outboard engines are usually a complete waste of money for commercial and government vessels.


Quite simply, they are not designed for anything other than recreational, or occasionally, racing use.

Outboard engines are usually merely petrol car engines turned vertically and connected to a modified automobile transmission. They were designed to provide the torque that an automobile requires in order to operate efficiently. The problems start to arise with respect to torque: Boats are under far higher levels of resistance than automobiles, particular at lower rpm ranges. So, many companies have tried to use diesel engines in outboards, rather than gasoline engines. What was the problem? Simple. The gearbox and drive systems were not designed to withstand the amount of torque produced by a diesel.

There is an old saying in the marine industry: “Horsepower sells boats, but torque actually moves them”. A quick glance at the marketing materials produced by outboard manufacturers quickly confirms that fact: Virtually none of them mention torque or show torque curves.

Some advantages of a diesel inboard over gasoline outboards:

  1. Diesel fuel is normally cheaper than gasoline in most markets. For example, in Australia, August 2015, retail price of diesel is A$1.29 per liter average, petrol A$1.34. In some countries the differential exceeds 20%. For instance, during the same period in Thailand, diesel averaged US$0.64 per liter and petrol US$0.93.
  2. Diesel engines always consume less fuel than gasoline engines. For instance, a Mercury Verado 350 consumes a whopping 353 g/kWh at full throttle, compared to 221 g/kWh on the Marinediesel VGT300. This equates to over 1/3 higher consumption. At cruising speed of 5,000 rpm on the outboard, the fuel consumption drops to 190 g/kWh, but the power produced decreases by over 1/3, netting just over 220 hp. The VGT300’s cruising speed of 2,800 rpm yields a fuel consumption of 195 g/kWh, but still producing nearly 280 hp.
  3.  As far as torque is concerned, virtually no comparison is possible. The outboard produces barely 400 Nm of torque, under a drastic bell curve, whereas the VGT 300 produces nearly 600 Nm of torque along the majority of the rpm range. A huge difference in actual work performed by the engine.
  4. Gasoline outboards have a MTBO of under 400 hours, light recreational use (all of them). A diesel inboard will last up to 3,000 hours MTBO. You could overhaul an outboard five times before needing to overhaul the diesel.
  5. The outboards are lighter. 303 kg versus 515 kg. This is reflected in their lower torque produced.
  6. However, space is less of a constraint. The Mercury Verado 350 is less than 100 mm smaller on all dimensions. A quick look at the photo above shows a transom width of about 1 meter. The VGT engines will require approximately 300 mm more length, and no extra width. A mere 300 mm extra height is necessary. In other words, on the boat picture, two VGT engines WILL fit.
  7. Outboards cost less to purchase. MSRP on the Mercury Verado 350 was US$32,000 in August 2015. The VGT 350 MSRP was US$37,000. However, given the fuel cost and consumption differentials, this small difference in acquisition cost quickly disappears.
  8. Gasoline is far more explosive than diesel. The inboards are much safer.
  9. Diesel engines have higher maintenance costs, but require much less maintenance.

As is evident in the points above, a strong case can be made for equipping your vessel with the Marinediesel VGT Series instead of outboards. The cost differential at acquisition is minimal, and the diesels far outperform outboards in nearly every instance. In particular, on the higher horsepower outboards, the price differential starts becoming significantly less.

Finally, in the picture above, twin Yamaha 200 hp outboards are pictured. A single VGT 400 or VGT 450 will outperform those two engines, lessening the price differential, even after gearboxes and drives are taken into account on the VGT engines.



VGT: THE diesel alternative to outboards

Outboards are common on small, high speed craft. Indeed, on some vessel types, they are often though of as the “default” propulsion method.


  1. They are cheap.
  2. They are easy to maintain.
  3. They provide “pretty good” speed.
  4. They do not take up much space.
  5. They are lightweight.
  6. A row of them, side-by-side “looks” fast and impressive.

However, outboard engines have some serious disadvantages and limitations:

  1. Outboard engines are usually gasoline automobile engines that are mounted vertically to a gearbox and drive system as a single unit. The forces generated by these engines are vertical, rather than horizontal, resulting in a substantial loss of power and a drastic increase in wear.
  2. Gasoline (petrol) is an explosion and fire risk, especially with government vessels or those used in the offshore industry. (Diesel is a much safer fuel)
  3. Gasoline is usually more expensive than diesel. Additionally, gasoline engines always consume fuel at a higher rate than diesel engines. (In some markets, the differential is as much as 50%).
  4. Outboard engines have a life cycle that is usually no more than a few hundred hours, at best. (You can  easily replace an outboard five times before needing to rebuild a VGT engine… Not so cheap now, eh?)
  5. Outboard engines are, by their design, limited in the number of propulsion options (You get what you get. With a VGT engine, you can use jets, surface drives, a variety of stern drives, or traditional shafts.)
  6. Diesel engines provide far more torque than outboard engines (Outboards cannot even come close).
  7. The vessel will always perform better with a VGT engine and proper propulsion system. ALWAYS.

The Marinediesel VGT Series of engines was designed to be the lightest, most powerful engines in their class. Our compact size and high power output make them an ideal alternative to the use of outboard engines. The VGT will, quite simply, fit where other engines may not.

Vessels can be equipped with Marinediesel inboard VGT engines at only a slightly higher cost than equipping the same vessel with large outboard engines, and that slightly higher cost is recouped very quickly in a much longer service life and the substantial fuel savings received. In fact, on larger outboard vessels, the use of outboards for propulsion is often equated by simply flushing money down the drain. They always cost more in the long term. In fact, many of our customers refer to outboards as “throwaway” engines. They run them full throttle until they simply break, and replace them with a new engine.


This “ease of replacement” and “ease of repair” is very much an illusion. The Marinediesel VGT Series will last up to five times longer than the average outboard before requiring an overhaul. Additionally, our remote mounting options give the VGT Series an ease of maintenance that approaches even the best designed outboard.

Additionally, the higher power and torque give a much better level of performance and control than an outboard-equipped vessel. Outboards, by design, are limited in the amount of operational control that they can provide, particularly regarding trim. A well-designed propulsion package with inboard engines will give a higher level of control and speed than even the best outboards on the market.

Finally, outboard engines are external, and thus, noisy by design. They are very difficult to control noise, and are often impossible for effective noise control.

If you want to look into the feasibility of using our VGT engines instead of outboards, and experiencing the meaning of true performance, Contact Us or your local Marinediesel Distributor for a quote today.


Oil Change Intervals – VGT Series



Perhaps the most common and critical maintenance procedures on any marine engine are the procedures related to filter and oil changes. Oil breaks down under use and heat, and changing the oil according to the specifications in the manual is important in adhering to the conditions of your warranty. The standard oil change interval for our VGT Series is 100 hours.

However, we are occasionally asked by customers if this interval can be extended. The answer is, “Yes”, under certain conditions described below. The interval need to change oil is primarily determined by both engine load and environment.

MarineDiesel’s VGT series marine engines have a standard oil change interval of 100hrs, however this has been selected due to variables in regional use such as load cycles, quality of fuel and lubrication oil etc. It is allowed to extend the oil change intervals under certain conditions; these must be closely monitored and given written approval by an authorized Marinediesel distributor.

The extended oil change intervals are only allowed on applications that have a predictable usage cycle, for example you are not allowed to perform below tests on a 200hr cycle where the engine is used at idle to then drastically alter the usage after extension approval.

Follow the recommendations below:

At 100 hrs: Take an oil sample and send to get it analysed. If the oil comes back as good to use then continue operations for another 50hrs. Top up engine oil if needed
At 150 hrs: Take an oil sample and send to get it analysed. If the oil comes back as good to use then continue operations for another 50hrs. Top off engine oil is needed.

Next 50hr check: Same as above

The maximum allowed oil change interval is set to 250hrs but this is not possible for all applications as oil tests may show.

Use oil and filter as specified in the engine technical manual.

If you have any questions regarding this break-in procedure please consult the technical department at Marinediesel in Sweden.





Our VGT Advantage



Today’s post is simply intended to explicitly describe the advantages of our VGT Series of engines over those made by our competition. We engineered these engines to be the lightest, most compact, powerful, and reliable marine engines in their class. See for yourself! All of these claims are well-documented and certified results are available on request.

  • The VGT Series, at only 515 kg, is far lighter than those made by our competitors.
  • The VGT Series is the lowest vibration level of any engine in its’ class. We manufacture the only V-8 alternative in this range in the marine market.
  • The VGT Series is the quietest engine in its’ class. Our engines are as much as 20 dB quieter than others in the market.
  • The VGT Series uses programmable NIRA ECUs. This makes the engines the only ones in the marine market that are 100% bespoke to performance requirements. Try getting that from our competitors. You simply cannot.
  • The VGT Series is the most compact engine in its’ class. We fit where others simply cannot.
  • The VGT Series produces the highest level of continuous torque along the greatest RPM range in its’ class. No competing engine even comes close.
  • With a MTBO ranging from 2,500 hours to 3,000 hours, the VGT Series has the longest life cycle in our market. Our competition tends to rate engines solely for recreational use. Our rating assumes heavy commercial or government use as standard.



VGT Series Break-in Procedures

When engines are new, they require certain break-in, or run-in, procedures before they are subjected to heavy use. The reason is that, though the engines are tested at the factory, seals and gaskets need both heat and time to form a good seal, and the engine needs time to properly lubricate. If proper break-in procedures are not followed, severe engine damage can result.

Below is the procedures for our VGT Series of engines.

The Marinediesel VGT series engines need break-in time before being operating to its full potential. This is due to the design characteristics of the base engine.

Follow the recommendations below:

0-5hrs: Use varied load and rpm but do not load the engine above 50% throttle and keep maximum rpm below 2500. Do not stay at one load and rpm configuration for more than 30 minutes at a time.

5-10hrs: Use varied load and rpm but do not load the engine above 60% throttle and keep maximum rpm below 2800. Do not stay at one load and rpm configuration for more than 30 minutes at a time. A few short WOT trials up to 3600 rpm is allowed for performance trials

Do an oil and filter change after the engine has run a total of 10hrs.

10-30hrs: Use varied load and rpm, the engine can be used up to 100% throttle and full rpm for shorter periods. Do not stay at one load and rpm configuration for more than 30 minutes at a time.

Do an oil and filter change after the engine has run a total of 50hrs.
Use oil and filter as specified in the engine technical manual.

If you have any questions regarding this break-in procedure please consult the technical department at Marinediesel in Sweden.



515 Kilograms


515 Kilograms. That weight is the equivalent of:

  • An average adult polar bear
  • 1.1 times the weight of a grand piano
  • 30% of the weight of an average sized sedan
  • About 10% of the weight of an adult Tyrannosaurus Rex
  • 12 times the weight of a toilet
  • The weight of MarineDiesel’s VGT Series of marine engines

MarineDiesel manufactures the lightest, most compact, most powerful marine engines in their class. No competitors even come close. Though the comparison above is somewhat lighthearted, vessel displacement is a highly critical factor in vessel performance, and MarineDiesel leads the way in high power at low weight.







Variable Geometry Turbocharger Facts


MarineDiesel’s VGT Series of engines was named as such for a very good reason: We use Variable Geometry Turbochargers (V.G.T.) in their design.

What is a VGT?

A VGT is a type of turbocharger that has internal vanes that open and close, changing the amount of air and exhaust that enter the engine. Thus, the geometry of the turbocharger changes, based on RPM.

Old, non-turbocharged diesel engines that are naturally aspirated were inefficient. Adding a turbocharger increased the amount of power and torque produced by the engine. By changing the geometry of the turbocharger, the compression ratio can be changed, thus making the engine more efficient, and substantially increasing the amount of power and torque produced, particularly at the low RPM range. Additionally, standard turbochargers tend to produce a lag at low RPM. The VGT solves this problem by further compressing the air into the engine.

The use of the VGT produces higher, sustainable torque across the engine speed range. In part, this is why our VGT Series of engines has a much higher level of overall torque, rather than the spikes, peaks, and valleys common in the toque curves of engines made by our competitors.

Since the power of the engine is increased by the VGT, it means that we produce, at only 515 kilos, the lightest, most powerful, 500 hp marine engine on the market.

Honeywell (the manufacturer of the Garrett VGT we use), has an interesting video that has an explanatory animation. We hope you find it interesting.





The VGT Series and Cadillac One: One thing in common


A little bit of trivia for a Monday morning:

The United States Presidential Limousine, dubbed Cadillac One, shares a common component with the MarineDiesel VGT Series of engines.

That common trait is that both use the Duramax 6.6L diesel engine block for their power. Though much of the limousine’s detail is secret, one thing that was publicly disclosed is the engine. Think about it for a minute. The vehicle has an enormous amount of weight from armor, security, and other devices. An engine block that is lightweight, yet powerful enough to move such a heavy vehicle is quite a useful thing to have.

This same power and light weight is even more important at sea. You can trust the fact that with MarineDiesel, you are getting the highest level of performance possible for your vessel.

Contact us today for a free, no obligation quotation.






Keep Calm and Get Torqued


For the last year or so, a popular meme has been making the rounds through Facebook, and so on.


This was originally based on a poster from the UK that was made during WWII, but never actually used. A few years ago, someone found it, and the image spread all over the Internet.


So in the spirit of perpetuating a modern legend (or irritation, depending on your viewpoint), here at MarineDiesel we invite everyone to Keep Calm and Get Torqued.


Because the engines you have been using are weak. They don’t have the power.

Because the MarineDiesel VGT Series gives your vessel the highest level of torque, at the lowest weight, in the market today.

Because you demand high performance, at a reasonable price.

Because you should never settle for second best.