# Propeller calculation

Discussion in 'Boat Design' started by Sarfaraz Manjra, Jan 28, 2019.

1. Joined: Jan 2019
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### Sarfaraz ManjraNew Member

Currently I am an intern working to a design an electric boat with a load of 350 KG . To select the right motor I needed calculations for the thrust and torque of prop. i have tried searching sites for formulae but couldn't understant. Please can someone tell me the exact way to approach for my problem .

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### PammieSenior Member

3. Joined: Jan 2019
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### Sarfaraz ManjraNew Member

No this is different thing. These are not the calculations i need.

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### gonzoSenior Member

Before calculating a propeller, you need to calculate the resistance (drag) of the hull at the target speed.

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### Squidly-DiddlySenior Member

I gotta question:

Say you have a 300hp motor, and need to power a 30ft typical deep V planing hull that will weigh 4 tons (or whatever is a pretty typical setup of motor and hull).

Which would go fastest: inboard/outboard, outboard or inboard(traditional shaft)?

And about how much diff between those motor setups?

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### gonzoSenior Member

I would say that it would be an inboard or outboard with surface piercing propellers

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### JSLSenior Member

some particulars on your boat and the speed you want to achieve would help: Otherwise, we are all guessing

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