What is a marinized engine?

In a recent issue that included a story on repowering, we wrote that Volvo marine marinizes Kubota engines for some of its engine offerings. This point brought a response from Stanley Feigenbaum, one of the founders and former owners of Beta Marine engines in the U.S., who informed us that Volvo uses a diesel engine manufactured by the Shibaura engine company as the basis for some of its marine engines. This was helpful, but it raised the question: what exactly does marinizing an engine mean and why is it important? 

It’s no surprise that the marine engine market is significantly smaller than many other engine market segments. Auto and truck manufacturers, for example, manufacture vehicles in the millions — according to the website Statista.com more than 78 million vehicles were manufactured in the world in 2020. This is somewhat more than the number of new voyaging boats built and repowered! 

So, a company like Beta Marine doesn’t manufacture its own marine diesels from top to bottom. It purchases a base engine — the block, crankshaft, pistons, valves, head, etc. — from an engine manufacturer. In the case of Beta, that manufacturer is Japan-based Kubota, which produces millions of engines a year that are used in vehicles, tractors, generators and more. When Beta receives the engines in its UK facility in Gloucester, it is just the base engine. Then Beta does the marinization. This essentially means attaching a wide variety of parts. “A standard engine is not going to do anything for you,” Feigenbaum said. 

Beta mounts a flywheel housing, a connection to the transmission, damper plates, raw water intake, fuel filter, air filter, heat exchanger, sea water pump, flexible engine mounts and a variety of other parts. These are all parts that turn the basic diesel into a true marine engine designed to operate in the marine environment. 

After each engine is fully marinized, it is put on a test stand and run through tests to make sure it operates properly. Then the oil and coolant are removed and the engine moves into the paint shop where Beta engines, for example, receive their distinctive red paint job. While the red is useful as a branding tool for a company like Beta, it also serves another purpose. “The painting shows warranty issues,” Feigenbaum said. If, for example, enough time has elapsed for the zinc anode to be replaced, but it still shows the original red paint, then Beta knows that a new zinc hasn’t been fitted. 

According to Eric Rydzewski, a semi-retired engine mechanic, surveyor and consultant in Wilmington, North Carolina, the key to a successful marinization doesn’t lie with the standard parts of a diesel engine like the piston, cylinders, block, head, etc. “It doesn’t need much change from the base engine,” Rydzewski said. “It’s mostly adapting the cooling system for a marine engine. How well that is done is the difference between a good or a not so good one.”

While an air-cooled exhaust can work for a diesel used on land, a marine engine that uses an air-cooled exhaust would get very hot and could start a fire in the engine room. A sailboat engine needs water cooling and it needs to be engineered with corrosion in mind. “All exhaust needs to be water-cooled, needs to be compact, corrosion resistant and be accessible for service,” Rydzewski said. “It can become a maze of tubes and hoses and has to be packaged correctly or you’ll have a mess in your engine room.” 

Engine and systems expert Steve D’Antonio (stevedmarineconsulting.com) says the biggest weaknesses in engines that haven’t been marinized well are seen in the attached systems. “Brackets that support alternators, heat exchangers and other components, they vibrate, crack and then fail,” D’Antonio wrote in an email. “Plus, poor routing of and support for wiring and hoses.”

And when looking to buy a diesel auxiliary engine for a voyaging sailboat, for example, D’Antonio had this advice: Vet manufacturers using the following criteria: 

• Dealer network: Will you be able to get service and support easily in your cruising grounds?

• What’s tech support like? Do you get a response to emails or phone calls, or are you just a number shuffled through a phone tree or email form? 

• Cost and availability of parts: Call a dealer and ask about availability (is it in stock?) and cost of a raw water pump, exhaust elbow and heat exchanger for the model you are considering, and compare.

• Ubiquity: if there are a lot of them out there it’s a good sign, if it’s one out of 50 on the dock, that represents greater risk. When a manufacturer makes a lot of any one thing, the bugs tend to get worked out more quickly. Higher production usually means lower cost, too. 

• Talk to a few people who have that engine with more than 1,000 hours on it. Has it been reliable? Have they been able to get support?  

By Tim Queeney