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##While their levels or curves are not parallel, horsepower and torque are both directly related to engine rpm.

abbreviated as hp(I). There’s not much of a difference unless you are talking about really large ship or locomotive engines. Occasionally, these suffixes may still be used on European and other foreign engines; however, with the adoption of European Union standards for member countries, all horsepower must be rendered in Watts (hp may be provided as well) for engines produced or sold in those countries, coming full circle to Watts, or kilo-Watts or kW, which equals 1000 Watts. One horsepower is equivalent to 746 Watts, or 0.746 kW. Therefore, a 100 hp(I) engine produces 74.6 kW.

##An engine’s horsepower is related to a variety of factors, from cylinder displacement and fuel injection system design, as well as rpm. Smaller, more powerful engines have become readily available thanks to an increase in rpm.

Th e r e ’ s H P a n d t h e n t h e r e ’ s H P That is not the end of the horsepower story. In addition to defining horsepower, its form of measurement must also be defined, and there are several definitions, including drawbar horsepower (dbhp), used for measuring locomotive power plants; indicated horsepower (ihp), a theoretical measurement of a perfectly efficient engine; brake horsepower (bhp), commonly used in marine and other applications to measure an engine’s power without any accessories such as transmission, belts, water pumps, hydraulic-power take-off pumps, etc.; and shaft horsepower (shp), a measurement

of the power available at the transmission output coupling. For the most part, the latter two are most commonly used for measurement of marine engine “power”; although, it’s important to understand that in both cases “accessories” such as alternators and pumps are not included in most engines’ hp ratings, and none of them take into account drag induced by shafts, stuffing boxes, or cutless bearings. Although it varies, the friction losses imparted by the transmission are typically between three percent and 10 percent, with reduction gears and V drives leaning closer

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