The right choice of engine revolutions transmission is another key element from the point of view of performance and drive effectiveness. The following elements have an influence on transmission:

• engine revolutions (rpm)
• power to weight in tonnes ratio (hp/t)
• speed of advance or  Froude coefficient (V/LWL0,5)

Where:

V – speed in kn
LWL – waterline length (in feet)
P – total power of drive units
W – total weight in tonnes
RPM – engine revolution speed

Assuming that  V/LWL0,5 coefficient is higher than 1 and the total power is higher than 100, the following formula may be applied:

R= 1,45 x exp((0,0034xT))

Where T=RPM/P/W

There are several significant gearbox providers  – the most renowned one is the German ZF, and Kanzaki, a slightly cheaper manufacturer cooperating with Janmar.