24v 120lb DIY brushless motor project

4HP = 3Kw. As long as you get the same power, the boat will reach the same speed. Was it going 5 mph before?

 

Hi Gonzo, Actual I have a different view. I always understood that the Hp from a petrol/gas/diesel engine is given by the manufacturer as the power measured at the propeller shaft. However the power from people making brushless motors, there is the power actual the battery consumed power and is thus less by the factor of the efficiency of motor and controller together and is normally whatever people are stating and bragging, about 90% . Thus for me, 4 hp petrol is not the same as 4 Hp (2,983 Kw) electrical power. Except if 3,3 Kw ( 4,4 Hp) power is applied to the motor. Sorry to trow a spanner in a widely argued topic. The only advantage I see is, that a brushless motor has its maximum torque at 100% at very low revolutions to maximum revolutions, and that is not the case with a petrol/gas/diesel engine. Gonzo, I am not arguing, I just have a good laugh that we all have been tricked for the same conversion 1:1. Bert

 

Bert, your explain is objective and unbiased. Same HP, petrol/gas/diesel engine use shaft power, but electric motor use input power. For same boat, petrol/gas/diesel engine surely will be quicker. But electric motor can thrust more heavier boat due to his larger torque. Brushless motor's advatage are its high efficiency which can over 65% and torque.

 

I am a brushless motor lover and fan. I love brushless motors, but the manufacturers must go away from comparing HP with KW. Ocean Volt had the story that a substantial higher HP is the same as a much lower KW brushless motor. We should go away from that. One should indeed look at the size and weight and required speed of the boat and then give a KW rated and KV rated motor. In that case there will be no misunderstandings or open for arguments. Bert

 

Right, I agree. We had changed our advertising words. Now we only use Input Power and Thrust etc.

 

I can see how that will create confusion. Probably I deal more with industrial motors that have both ratings: input and output power. Otherwise, they would be impossible to size for a machine.