"Injam" wrote in message
k.net...
Why? If the propellers are turning at the same RPM and they have the same
pitch, why would the 250 hp be faster?


"Harry Krause" wrote in message
. ..
Injam wrote:
Hello,

I'm trying to understand propellers.

If you have two identical boats, but the outboard horsepower ratings
are different. One boat has a 200 hp and the other a 250 hp. Both motors
have the same Gear Ratio. If the propellers are identical and the RPM of
the outboard is the same on each boat. Say 6000 RPM. Because of the
weight advantage will the 200-hp boat be faster than the 250 hp? I'm
thinking less weight less slippage otherwise they would be going the
same speed.



Sincerely,

Injam




If the 200 hp engine is properly propped, the 250 hp engine will most
likely be underpropped with the same prop. The weight diff between a 200
hp and a 250 hp is not usually significant, certainly not enough t0 canel
out a 25% increase in hp.

Now, to your question...the 250 still might be faster, even if it is
underpropped.



It will be faster to the same speed. But, the 2 engines should not have the
same pitch prop. The 250 hp will overspeed with the correct pitch for the
200 hp. Same pitch and same RPM, other than a weight difference, both boats
would be the same speed.