It’s Exhausting

Marine exhaust systems are actually fairly complex systems: much more complex than a layman would think. They are simply the “tailpipe” of the boat, right?

This misconception is often a problem. One critical part of the vessel exhaust system is the exhaust risers, and these can often fail. The function of the riser is two fold:

  1. They keep water from backing up into the engine.
  2. They channel cooling water to the engine.

The design of the exhaust riser is critical, and is a situation where it often is beneficial for the engine manufacturer and the shipyard or naval architect to work closely together. If the angle of the riser is incorrect, or it is modified, water can accumulate, leading to bad corrosion issues. Poor design, especially with aftermarket additions or modifications, can also create serious back pressure problems on the engine, greatly impacting engine performance.

Water and metal do not mix well. This is why the gaskets and the risers should be frequently inspected and replaced if necessary. Even in cases with no leakage, the risers should be removed and periodically cleared of any rust or scale that may have formed.

Some engine manufacturers provide risers with the engines, and other do not (they are optional with Marinediesel). In some cases, they must be custom designed in order to fit into an engine compartment. In any event, there is a golden rule with exhaust risers: NEVER use aluminium risers. Yes, they are cheap, and risers can be one of the more expensive components to buy, but they are short on life span and can cause serious problems over the life of the engine.

Power Take Off

Marinediesel offers various PTO options with all of the engines we manufacture. In fact, the list of applications would be quite large, were we to list them all. Some examples of PTO options we have provided in the past, for both marine and industrial uses include:

  • Alternators
  • Pumps
  • Hydraulic Motors
  • Fire Control Systems
  • Blower Systems
  • Lifts, Davits, and Cranes

In fact, PTO is a standardized option, and a variety of shafts and couplings can be provided, depending on the use. You need merely ask your dealer or distributor to add it to your purchase and we will do the rest!

MD VGT + Jackshaft closeup

At what point does saving money become a project?

We all want to save money. Sure, it is human nature to spend the least, but get the most. However, there is the old idiom about being “Penny wise, but Pound foolish”, often incorrectly attributed to Benjamin Franklin, that often applies when comparing options.

We once had a suspiciously large parts order from a new, unknown customer. When the parts department received the order, they were perplexed: When did we sell an engine to these guys?

They combed through our accounts history and found nothing. What was going on?

It turns out that the customer had been given a GM engine block on the aftermarket (an old GM truck engine) and was trying to marinize it himself to use it on his boat. There are a number of different reasons why this is not a good idea for the average home mechanic, no matter how experienced or no matter how good his mechanical aptitude:

  • Most workshops lack the facilities for proper marinization.
  • You generally cannot use automotive parts in a marine engine, due to corrosion issues.
  • Marinization is a highly technical process. Without experience, the process can quickly become complicated and expensive.
  • Engines perform differently on the water than on land. The power and torque curves are completely different, and on an electronic engine, significant software knowledge is required.
  • Modern emissions requirements are tricky. In some locations, operating a vessel without certified emissions is illegal. It is very difficult to meet emissions requirements without the proper testing facilities.


Most of all….

Marinediesel, as a manufacturer, has certain economies of scale when purchasing components. Quite simply, when you buy thousands of injectors, you pay much less than when you are buying two. Additionally, though it really isn’t a secret, most manufacturers make most of their profit from spare parts and service, rather than from the sale of the engine. That is why there is usually a big difference in markup on spares, but very little difference in price between similar engines (ie. Volvo Penta D6 vs Marinediesel VGT 400).

In the end, he was a little shocked that refurbishing his old engine would end up costing almost as much as a new engine. We finally convinced him that he would spend so much time and money that he really would save very little in the end, and most likely end up spending more. A project, indeed…

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.

Video: Airboat with MDPT Engines

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.



Maintenance Tip of the Week: Fuel Filters 11/02/2015

Maintenance Tip of the Week – Fuel Filters 11/02/2015

Always use the correct size of fuel filter, as specified in your manual (most Marinediesel engines require 10 micron size). Incorrect, or cheap, fuel filters can seriously damage your engine, especially in locations where fuel quality is a problem. Inexpensive fuel filters are often of poor quality and are usually not much cheaper than quality brands.

Equip a Fleet and Save Money

Marinediesel are seldom the cheapest engines in our class in the market. Indeed, we usually are priced somewhere in the middle: Not the cheapest, and not the most expensive, either. We do, however, feel that we give our customers much more value for their money, due to our technical advantages:

  1. Highest power to weight ratio: More power for the same money.
  2. Longest life cycle: Our competition cannot even come close.
  3. Lowest noise and vibration: The Laws of Physics mean that we will be quieter, with less vibration than any of our inline six cylinder competition.
  4. Remote diagnostic capability: Our technicians can diagnose your engine, anywhere in the world from our factory in Sweden.
  5. Customized performance: Go ahead. Ask Yanmar to customize an engine and get back to us on that.

These advantages make a solid case for Marinediesel well above any minor price differentials. However, we ask you to take a look at the web sites of any diesel engine manufacturers.

How many list prices online?


There are very good reasons for this.

  1. There is nearly always a distributor involved for all but the most customized engine (like racing engines, which are manufactured annually in the dozens, rather than thousands or tens of thousands). Distributor involvement is an absolute necessity from a service perspective and for spare parts.
  2. VERY few people simply purchase a bobtail engine. Most engines require a certain amount of ancillary equipment in order to  be installed. Simply comparing bobtail prices is inaccurate and pretty much useless.
  3. Volume. It costs less to supply 100 engines than two engines.

This last point is pretty important. When you equip a fleet of vehicles with a specific engine, it is normally much cheaper than simply equipping one or two vessels. It costs Marinediesel, as the manufacturer, less to make the engines, and we pass those savings on to our customer. This is why bulk purchases are usually much cheaper on a quantity basis. It really is not much different than when one buys food at the supermarket. Big, family sizes, of products are usually cheaper than individual portion sizes.

On your next project, contact your local Marinediesel distributor for a quote. Our distributors often have a great deal of price flexibility and we will work with them to provide you the highest performance possible at the lowest price possible.


The Continuous Duty Conundrum

AnytecCIMG1379 (2)

Thinking back to the old business school days, one of the first things that is taught in marketing classes is the use of “spin” in getting one’s message across to the consumer.

What is spin?

According to Merriam Webster:  a certain way of describing or talking about something that is meant to influence other people’s opinion of it.

Or, to put it more bluntly, a form of propaganda.

Here in the Marinediesel marketing department, we are always exposed to different levels of “spin” put out into the marketplace. Indeed, as an engine consumer, spin can be confusing, and is, by nature, misleading.

One of the most common areas to encounter spin in the diesel engine market is with regard to engine ratings. Though it may surprise you, there is very little regulation in determining the actual meaning of engine ratings. In fact, as an engine manufacturer, we (or any other manufacturer) are not required to define terms like “light duty”, “heavy duty”, or “continuous duty”. We are only required to tell you the true output of the engines based on measured and tested power and torque, at specific rpm levels.

Therefore, the engine ratings game becomes an area that is often deliberately confused by engine makers, to their advantage, of course. To illustrate, Marinediesel’s definition of “light” duty might be something like “under 700 hours of operation at 80% WOT (wide Open Throttle)”, and another manufacturer might define “light” duty as “under 500 hours of operation at 50% WOT”. Are these definitions a lie? No. They are the parameters that the manufacturer establishes, and as long as they are consistent, they are valid. Are they spin? Most definitely.

This is how some engine makers are able to sell engines that are designed for recreational use to commercial, government, or military customers. The “heavy use” or “continuous use” ratings are, effectively, whatever the maker designates them to be.

Here at Marinediesel, we believe in being 100% open and honest about the capabilities of the engines we manufacture. This is why we often ask quite a few questions when we quote an engine. We would rather make certain that an engine is appropriate for its intended use than to sell something that is not a good fit. No marketing games with Marinediesel.

It becomes critically important that you, as the consumer, actually take the time to read and understand what the engine ratings advertised actually mean. If you need truly continuous duty, then let us know that you need continuous duty. If our engines are a match, or can be modified, we will give you a 100% honest answer.