Mercury MerCruiser - Diesel 3.0L

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Captain's Report

Mercury Diesel 3.0L V-6


The Mercury Diesel 3.0L is a lightweight clean-burning diesel engine that can be used in inboard, sterndrive and jet applications.

Overview


The Mercury TDI 3.0L diesel is designed to be a viable alternative for gas engines in small boats for both towing and fishing applications. This 260-hp engines weighs 675 lbs. (306 kg) and measures 35”L x 32”W x 34”H. Its weight including a transmission is 771 lbs. With a Bravo III sterndrive the total weight is 933 lbs. (423 kg). Its maximum ROM at WOT is 4000. The engine has a bore and stroke of 3.27” x 3.58” (83 mm x 91 mm).


Tough and Light. For strength and durability, the engine’s 3.0-liter block is made with a vermicular graphite casting that is lighter and stronger than conventional cast iron that is the foundation for so many engines. The head is made of aluminum.


Corrosion-Resistant. To protect the engine from corrosion, it has a closed cooling system with the reservoir mounted up high for easy access. Mercury is an industry leader these days in corrosion-resistance thanks to the use of special alloys, painting procedures, and stainless steel where necessary. The engine can be fitted with the SeaCore anti-corrosion package which has been proved over nearly a decade of use.


Mercury Diesel 3.0L V-6


The reservoir for the closed cooling system is mounted up high on the engine, making it easy to top off.

Under Pressure. Our test captain raved about the absence of turbo lag from the Mercury Diesel 3.0L under hard acceleration. Lag, or hesitation, has been a shortcoming with turbocharged diesels in the past. Mercury overcame it with direct fuel-injection that blasts highly atomized diesel fuel into the injectors at 26,000 psi to create more robust combustion and cleaner emissions. We never saw smoke from this engine, even at startup.


Mercury Diesel 3.0L V-6


Fuel rails pressurized at 4,000 psi help the Mercury Diesel 3.0L meet Tier 3 emissions standards.


Mercury Diesel 3.0L V-6


Here our test captain points out the fuel-pressure sensors on the back of the common rail that sends information to the engine control module.

Advanced Design. In addition to the high-pressure fuel system, the Mercury Diesel 3.0L’s turbocharger has a variable geometry design for high low-end torque, which is the secret to its noteworthy acceleration. A charged-air intercooler that reduces the temperature of the intake air, improves efficiency and power output.


Mercury Diesel 3.0L V-6


The turbocharger is designed to improve fuel economy and its low profile lets the engine fit into the same envelope as a naturally aspirated gas engine.


Total Control. In addition to marinizing the Volkswagen engine, Mercury configures the motor’s electronic control module to work with the SmartCraft management system, making it compatible with a variety of Mercury gauges and multifunction screens.
Mercury Diesel 3.0L V-6


The engine’s electronic control module is positioned for easy access on the front of the motor and is compatible with Mercury’s SmartCraft management system.

Convenient Access. An engine with accessories that are easy to get to will probably get better attention for maintenance so Mercury makes sure that equipment that should be checked regularly is in reach. The water pump is in a brass housing on the front of the motor while the oil cooler is down low on the starboard side. The oil filter is just above. Still to starboard, the heat exchanger is below the coolant reservoir that we already discussed. Finally, the fuel filter is down low to port and has a thumb primer in case the engine runs out of fuel.


Mercury Diesel 3.0L V-6


The oil cooler is down low on the port side of the motor and notice that there’s enough space to tighten the hoses with a wrench.


Mercury Diesel 3.0L V-6


The 3.0L’s oil fill is to port at the front of the motor and the filter is in the center of the engine, still readily accessible.


Mercury Diesel 3.0L V-6


The water pump is in this brass housing on the front of the engine.


Mercury Diesel 3.0L V-6


Located just ahead of the engine to starboard, the fuel filter has a thumb primer on top if it’s needed.

Digital Dash. As previously mentioned, the Mercury Diesel 3.0L is compatible with SmartCraft so it can work with a variety of instruments and multifunction touchscreens. The Epic 23v we tested had a VesselView 4 screen. The engine also works with Mercury’s Digital Throttle and Shift, which is especially critical when towing wake surfers at speeds as slow as 11 mph.


Mercury Diesel 3.0L V-6


Mercury’s VesselView 4 is one of the many SmartCraft compatible instruments that work with the 3.0L.


Mercury Diesel 3.0L V-6


The digitally controlled throttle gives the driver precise control when towing watersports.

Performance


Revved Up. We tested the engine as part of a V-drive inboard installation in an Epic 23v wake boat. With two people, slightly less than half a tank of fuel and two people aboard, test weight was 4,449 lbs. (2,018 kg). The 260-hp Mercury Diesel 3.0L V-6 turned a 14 ¾” x 16 ¾” four-blade bronze propeller through a 1.56:1 gear reduction and the engine revved up to an un-diesel like 4080 maximum rpm, hitting 33.1 mph and burning 10.6 gph, resulting in a range of 182 miles.


Best cruise came at 2500 rpm where the boat ran 18.5 mph and burned 4.3 gph for a range of 201 statute miles with 10% of the boat’s 52-gallon (197 L) fuel capacity in reserve.


Mercury Diesel 3.0L V-6


The turbocharged diesel engine delivered a strong combination of performance and fuel efficiency.

Acceleration. Watersports towboats are all about holeshot and acceleration and the Mercury Diesel 3.0L delivered plenty of both – as good as most gas sterndrive engines we have tested. The 23v planed in 3.2 seconds and continued to 20 mph in 5.2 seconds and to 30 mph in 7.3 seconds.


Mercury Diesel 3.0L V-6


Out of the hole, the 260-hp Mercury Diesel 3.0L had the punch that planted our test captain back in his seat.

Similar Size. The Mercury Diesel 3.0L V-6 weighs 675 lbs. (350 kg) without a transmission and has dimensions of 35” x 32” x 34” (927 mm x 813 mm x 853 mm). By comparison, the MerCruiser 6.2-liter (377 cid) TowSport Inboard that is available in 320-hp or 370-hp, weighs 862 lbs. (391 kg) without a transmission and has dimensions of 32” x 30” x 22” (813 mm x 762 mm x 559 mm). The diesel is taller, but Epic said it had no issues with installing the Mercury Diesel 3.0L V-6 in the same envelope. The only additional step required to rig the boat is adding a fuel return line, they said.


Mercury Diesel 3.0L V-6


The Mercury Diesel 3.0L V-6 fit in the Epic 23v’s engine compartment with minor modifications made to the motor mounts.

Lower-End Power. Diesel engines are known for their torque output and the 3.0L 260 is rated at 407 ft-lbs. (551 Nm) at 2000 rpm, 394 ft-lbs. (534 Nm) at 3000 rpm and 332 ft-lbs. (450 Nm) at 4000 rpm. The 230-hp version puts out 370 ft-lbs. (502 Nm) at 2000 rpm, 361 ft-lbs. (489 Nm) at 3000 rpm and 296 ft-lbs. (401 Nm) at 4000 rpm.


Mercury Diesel 3.0L V-6


Because of the torque output of the Mercury Diesel 3.0L V-6, Epic uses a 1.56:1 gear ratio in the V-drive transmission.

Propeller Choices. Because it makes peak torque at such a low rpm range, the Mercury Diesel 3.0L V-6 is packaged with a ZF63IV 1.56:1 transmission in the 23v. This allows Epic a wider range of propeller options to keep the boat running consistently at wake surfing speeds of 10 or 11 mph. The gas engines have a 1:1 transmission that limit propeller selection.


Mercury Diesel 3.0L V-6


The engine’s torque range gives Epic more choices when it comes to a propeller.

Price


The MSRP for the Mercury Diesel 3.0L V-6 260 is $33,533.


The MSRP for a Mercury 6.2L 320 ECT TowSports gas inboard is $20,550.


The MSRP for an Epic V23 with a MerCruiser 6.2L 320 ECT gas inboard is $79,941.


The MSRP for an Epic V23 with a MerCruiser 8.2 Horizon inboard is $99,345.


The MSRP for an Epic V23 with a Mercury Diesel 3.0L V-6 260 is $121,925.


Warranty


3-year Limited Warranty


Observations


We confirm that the Mercury Diesel 3.0L V-6 delivers the torque and fuel economy that the manufacturer touts. With its turbocharger, inter cooler and high pressure fuel system, it has an advantage over gas engines because it won’t “load up” while running at the rpm required to hold a watersports boat at 10 or 11 mph — the favored speed for wake surfing — for hours on end.


The elephant in the room is the price difference compared to a gas engine. It should be noted that watersports towboat owners often keep their vessels longer than owners of other types of boats. They also put a ton of hours on their boats skiing, boarding and surfing. If an avid watersports enthusiast intends to keep his boat for a long time, there is a significant fuel savings to be had.


The same could be said for owners who are restoring a classic boat and want to take advantage of the benefits the 3.0L V-6 diesel offers. Anyone planning to keep his boat for a while should also consider the added safety of diesel in addition to fuel savings accumulated over time.