Yanmar  - 4BY180

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Captain's Report

Yanmar 4BY2-180 Diesel Engine

By Captain Robert Smith

Yanmar has updated the BY series of engines that were introduced about 2 ½ years ago. These 150, 180, 220 and 280 hp in-line diesels now have a few improvements, yet maintain the same horsepower. I tested the 4BY2-180 on a fully restored Bertram Moppie 25 with Yanmar’s own ZT350 sterndrive units. Yanmar says this engine is designed as a re-power or OEM diesel for the single or twin screw application in the mid 20 foot plus range. It has also been popular in the trawler market. This engine is based on a BMW block that is marinized and assembled by a Yanmar plant in Europe. Yanmar has used weight saving materials such as aluminum top covers that are adequate for stepping on while providing protection. Yanmar also uses aluminum in the oil pan, intercooler housing, and heat exchanger; and plastic in the intake manifold. That weight savings has improved the power-to-weight ratio even more. This compact size engine can fit into a number of different applications, including a gas-to-diesel re-power application. The exhaust manifold is water cooled now. The heat exchanger now has a full metal cover that reduces overall height by 23 mm. The turbocharger is double insulated with a blanket and full metal cover. The BY Series engines meet both the EPA and RCD emissions standards.

The 4BY-180 is a sub-2 liter (1.995) fuel injected ECU controlled engine. It is a 4-cycle in-line 4 cylinder diesel with dual overhead camshaft. It is direct injected, turbocharged and intercooled. It has a maximum output rating of 180 hp/4000 rpm at the crankshaft and a continuous output at the crankshaft of 137 hp/3600 rpm. Maximum torque is 262 ft-lbs. and low idle speed is about 750 rpm. High idling speed is 4600 rpm. This engine has a 150 Amp alternator, is closed cooled and has a heat exchanger. Dry engine weight is 551 lbs. or 250 kg. This engine is typically mated up with a Kanzaki KMH40 marine gear, MerCruiser Bravo sterndrive or Yanmar’s own Kanzaki ZT350 sterndrive. The 4BY2-180 has two onboard fuel filters; a 10 micron fuel filter/water separator and a 3 micron fine particulate fuel filter.

When testing the repowered Moppie, I tested with a load of five, then a load of 2 onboard. The speeds were very similar with the best top speed being with five on board. I suspect that may have been related to something other than engine performance, but the bottom line is the Bertram 25 Moppie and the 4BY2-180 with ZT350 sterndrive seemed not to care about the load.

With five onboard, top speed was 44.3 mph or 38.5 knots burning 18.9 gph or 71.5 lph and delivering 2.34 mpg or 2.04 nmpg. Most economical cruise speed was at 2250 rpm and 21.6 mph or 18.7 knots burning 5.9 gph or 22.3 lph delivering 3.68 mpg or 3.20 nmpg for a range of 285 miles or 248 nautical miles.

The Yanmar 4BY2-180 engines ran flawlessly performing high speed turns and idle to 30 mph runs without hesitation. If you are looking to repower or spec your engines, you may want to check these out yourself before you make that final decision.