So you disagree with the rule of thumb that speed varies as the square
root of HP? I got the formula out of a Mercury High Performance Prop
book a few years ago. :-) How much do you think the speed will
increase with an extra 33% or 50 HP? I know you think a 200 will use
less gas putting out 100 hp than a 150 will. I'm open minded on that
question.

del

"Clams Canino" wrote in message
news:H9Yfb.45272$%h1.29399@sccrnsc02...
You did fine Gene. He was comparing apples and hammers.

-W

"Gene Kearns" wrote in message

Perhaps I did a poor job of making my point. Your rule of thumb
works
when one compares apples and apples....

Yes, once the carbs start to open, the closer you get to WOT - the more gas
it'll suck. What's more unclear to me is if the 115 and 130 (both 99ci) had
much of a difference. I only ran the 115 for a week or so. But it felt to
me like I needed less throttle to get the same speeds even then.

Another thing I could add - is that if you pull a lot of skiiers and toys.
Holeshot sucks gas. The shorter holeshot the better off you are. In that
respect, I'm *sure* I'm doing better with the higher output 99ci than the
old one. That's why I advise people to get the highest output version of
any one particular block. Since they weight the same anyway - might as well
get the most bank for the buck.

-W


"del cecchi" wrote in message news:rv2gb.198

However experience trumps extrapolation. It certainly seems true that
WOT blows the fuel economy.

del

I'm sorry - I wasn't dissagreeing with the speed part - just the fuel part.
But again I stress that getting the highest output version of *any
particular block* is "free hp" since the weight is the same. If you have to
get a heavier motor to go up - then you might be wasting time.

That's why I run the 99ci inline 6 as opposed ot the V-6's. My outboard
even with power trim is well under 350 pounds. If I want more HP, I'll soup
up my 99ci as opposed to going V. Those things were rigged to put out 90,
115, 130ish, 140, 150, and 160 at the crank. (with race stuff getting to
200hp) Anyone that bought that 90hp was just silly. LOL.

-W



"del cecchi" wrote in message
...
So you disagree with the rule of thumb that speed varies as the square
root of HP? I got the formula out of a Mercury High Performance Prop
book a few years ago. :-) How much do you think the speed will
increase with an extra 33% or 50 HP? I know you think a 200 will use
less gas putting out 100 hp than a 150 will. I'm open minded on that
question.

del

"Clams Canino" wrote in message
news:H9Yfb.45272$%h1.29399@sccrnsc02...
You did fine Gene. He was comparing apples and hammers.

-W

"Gene Kearns" wrote in message

Perhaps I did a poor job of making my point. Your rule of thumb
works
when one compares apples and apples....

On Sun, 05 Oct 2003 20:51:16 -0400, Gene Kearns
wrote:
I'm a bit mystified as to why I went from 150HP and a 13.75X17 prop to
140HP and a 13.75X19 prop and still run the same speed at top end!!
Not that this isn't quantifiable.... but I sure lack all of the
data...

==========================
Let's do the numbers:

SQRT 150 = 12.247

SQRT 140 = 11.832

The difference equals 0.415 which when divided by 11.832 equals about
3%. For a WOT of 30 knots, this means that you should have
theoretically gotten about 1 knot extra at the high end if everything
else matched up perfectly. The implications are that you need to
double the horsepower to go 40% faster, and that assumes no increase
in weight or drag which hardly ever happens. (SQRT 2 = 1.414)