A number of variations may include a thermal management system having an engine and a coolant system comprising a coolant circuit and a coolant pump, wherein the coolant pump is operated by an electronic control unit that operates independently of the engine, and wherein the electronic control unit is constructed and arranged to operate the coolant pump at a higher speed than the engine speed multiplied by pulley ratio during engine warm up.

A water pump unit has, within a water pump case, a drive shaft for driving an impeller, and a transmission member for transmitting power of a power supply device to the drive shaft. The water pump unit is configured such that the water pump case receives therein and supports the drive shaft, the transmission member is supported by the water pump case by means of the drive shaft with a part of the transmission member protruding from within the water pump case, and an attachment surface of the water pump case, for joining the water pump case to the power supply device, is formed to extend along the transmission member.

A water pump unit has, within a water pump case, a drive shaft for driving an impeller, and a transmission member for transmitting power of a power supply device to the drive shaft. The water pump unit is configured such that the water pump case receives therein and supports the drive shaft, the transmission member is supported by the water pump case by means of the drive shaft with a part of the transmission member protruding from within the water pump case, and an attachment surface of the water pump case, for joining the water pump case to the power supply device, is formed to extend along the transmission member.

An engine cooling apparatus includes a mechanical water pump having a suction hole and N discharge holes (N is an integer not less than two), N water jackets that are arranged in an engine and correspond to the N discharge holes, N joint passages, each of which joins one of the N discharge holes to the associated water jacket, a return passage that returns coolant to the suction hole after the coolant has passed through the N water jackets and has merged in a merging portion, a coolant stopping mechanism that blocks return flow of coolant through the return passage, and N communication passages each of which allows the corresponding one of the N joint passages to communicate with the suction hole while bypassing the N water jackets and the coolant stopping mechanism.

An outboard motor includes an engine, a first cooling water passage to cool a first cooling target including the engine and through which first cooling water including water from outside an outboard motor body passes, a first pump to pump the first cooling water from outside the outboard motor body to the first cooling water passage, a second cooling water passage to cool a second cooling target different from the first cooling target and through which second cooling water different from the first cooling water passes, and a second pump to pump the second cooling water to the second cooling water passage.

An outboard motor includes an engine, a first cooling water passage to cool a first cooling target including the engine and through which first cooling water including water from outside an outboard motor body passes, a first pump to pump the first cooling water from outside the outboard motor body to the first cooling water passage, a second cooling water passage to cool a second cooling target different from the first cooling target and through which second cooling water different from the first cooling water passes, and a second pump to pump the second cooling water to the second cooling water passage.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

In a vehicle power unit having an internal combustion engine, a pair of power transmission gears for transmitting rotation of a crank shaft to a balancer shaft is arranged between a crankcase and a crankcase cover, and a fluid pump is provided on a power transmission gear shaft supporting a power transmission gear, by which the backlash between the crank shaft and the balancer shaft is reduced and the friction and the noise of the gears are restrained while achieving downsizing of the gears of the crank shaft and the balancer, weight reduction and downsizing of the power unit.

In a vehicle power unit having an internal combustion engine, a pair of power transmission gears for transmitting rotation of a crank shaft to a balancer shaft is arranged between a crankcase and a crankcase cover, and a fluid pump is provided on a power transmission gear shaft supporting a power transmission gear, by which the backlash between the crank shaft and the balancer shaft is reduced and the friction and the noise of the gears are restrained while achieving downsizing of the gears of the crank shaft and the balancer, weight reduction and downsizing of the power unit.