- Both boats would be the same fast in Theory.
The same fast. Yes boats go same fast, Tarzan.
a. The 200 HP motor could not rev up to 6000 rpm IF its a prop for the
250
In my scenario the 200hp is turning at 6000 RPM.
b. If the prop is for the 200 HP motor the 250 would rev at 6000 not be
able to put more power in the water.
I don't even know what you are saying.
c. The 250 would accelerate faster until it has reached 6000 rpm and
there have the same speed as the 200 (if it can swing the prop).
The 200hp can (swing the prop), but because of it's lighter weight the 200hp
would pass the 250hp on are about the five mile mark. At the ten
thousand-mile mark the 200hp would be approximately five thousand miles
ahead of the 250hp.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Just having a little fun. Thanks for the post. I did figure it out and I did
post my conclusion. It is in this NG somewhere.
Sincerely,
Injam
"M" wrote in message
ups.com...
Injam wrote:
If we use a 24" pitch propeller and there was no slippage, both boats
would
travel 12,000 feet every minute at 6000 RPM.
With the same propeller on each boat the 250 hp boat would over rev at
WOT.
So the helmsman would have to back off to keep it at 6000. The difference
in
weight of the motors is about 30 lbs. Probably not going to be much of a
factor. The 250 might get to 6000 more quickly, but once at 6000 I think
both boats would be traveling at the same speed.
Thanks again,
Injam
"Injam" wrote in message
news
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.
Depending on what brand motor you have they will even weigh the same...
even if not the little difference in weight will not make a difference.
Here is how it goes:
- Both boats would be the same fast in Theory.
- In reality one of these will happen:
a. The 200 HP motor could not rev up to 6000 rpm IF its a prop for the
250
b. If the prop is for the 200 HP motor the 250 would rev at 6000 not be
able to put more power in the water.
c. The 250 would accelerate faster until it has reached 6000 rpm and
there have the same speed as the 200 (if it can swing the prop).
A similar question is:
"Is a 250 HP 2 stroke or 250 HP 4 stroke faster?"
answer is: They will reach the same top speed but the 2 stroke will
likely accelerate faster.
In reality acceleration and top speed may be different as both will be
propped and geared differently and have different torque curves. But
for top speed its peak HP that matters.
Matt