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VP 280

"The lower the torque of an en

"The lower the torque of an engine, the higher the gear ratio that is needed between the engine and the propeller. 4-cylinder engines only develop power at higher RPM, but their torque is small. Therefore, they need a higher gear ratio so that enough torque is transmitted to the prop. Meanwhile, V6 and V8 engines have far more torque than a 4 cylinder, so a lower gear ratio is required. Furthermore, the gear ratio must be such that the propeller can absorb full power at WOT, but the engine is not overloaded in the mid-range.

Mercruiser has typically used 1.50:1 for V8 applications, and Volvo (for whatever reason) has chosen the 1.61:1 ratio. My advice to you is that you stick to the manufacturer's recommedation, as they designed these gear ratios for good reasons."
 
Because you can't usually

Because you can't usually get a prop pitch that will allow the engine to achieve rated full RPMs at wide open throttle...
 
Thank you. One more question p

Thank you. One more question please. 2.15:1 ratio = prop shaft 2.15 turns to 1 engine rev?
 
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