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Discussion Starter #1
ok guys this is only my second thread so please be nice.

i am daydreaming at work about the project i might be about to undertake and i have something i dont understand.

IF.. my buddies 19 foot mastercraft ski boat will run 50ish with a stock 351.......why does it seem to take such extreme big block hp to get these flatties to scoot?

maybe im comparing apples and oranges and maybe 50 is like sitting still to you guys...

i have been feverously searching and reading on the internet and im still lost.
 

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HP to MPH curve

has about the same slope as a redwood tree:D

Any racer with a clue will agree that the first few MPH are easy to gain , after that the wallet get thinner much quicker than the boat goes faster.

infact i may have stumbled upon the pythagarean theorem of racing...... wallet - $$$ = speed :)coffee


pat
 

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kinda similar to drag racing i suppose.....pretty cheap to get under 10s.... kinda expensive to get under 9s.... second mortgage to make it under 8s....
 

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next question.......

what makes a marine engine a "marine" engine?

can i build a big block and just use different gaskets, seals, etc. than i would use for the street?
 

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next question.......

what makes a marine engine a "marine" engine?

can i build a big block and just use different gaskets, seals, etc. than i would use for the street?
IMO, the only difference is exhaust and sometimes cam choice. Some marine components like electric fuel pumps, msd boxes and carburetors may last longer because they were made using corrosion resistant parts.

Just my .02
 

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As far as marine vs automotive applications go, there are those who subscribe to the theory that clearances need to be different. With expansion and contraction being a bigger issue on the water and the introduction of water being 70 degrees or less rather than a well warmed 180 degree radiator feeding the cooling system. Of course the blueprint of a boat motor differs greatly from asphalt applications. Props are designed to slip where tires actually aren't so much. Torque and horsepower curves differ as a result. The absolute fine tuning comes at the top of the racing circuits where every application of the boat matter more and more. There are single carbureted SS boats that shame some blown K-Boats to prove my theory. If you are not racing with the best, just build something that pleases you, try a few props/gear sets and when you get the combination you like best, stick with it. Definitely, don't hesitate to ask for starting points from others with similar applications as you are running. You'll be glad you asked. As Jerry so aptly reminded us there are some who spend $100K a year to stay ahead of the pack. My opinion after watching them for years and years is that it has been money well spent - for their desire to run out front?
 

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ok guys this is only my second thread so please be nice.

i am daydreaming at work about the project i might be about to undertake and i have something i dont understand.

IF.. my buddies 19 foot mastercraft ski boat will run 50ish with a stock 351.......why does it seem to take such extreme big block hp to get these flatties to scoot?

maybe im comparing apples and oranges and maybe 50 is like sitting still to you guys...

i have been feverously searching and reading on the internet and im still lost.
Some stupid simple math with a lot of assumptions: The max speed of a car is limited by the torque made by the engine multiplied by gear ratios, etc. being simultaneously equal to the aerodynamic drag at max speed. The same goes for a boat, but the dominate retarding force is hydrodynamic drag. For either, the force required increases as the square of speed, that is to go twice as fast requires 4 times the force (torque). The difference between the two is the density (which appears as a linear term (not squared) in the relationship is greater for water than air.
Flame away.:D
 

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boat speed theorem V1.1

allow me to revise, if you will

thick wallet - $$$$ + (time)squared = boat speed

a lot of other factors will sway the results
The magnitude of the "man orbs" possessed by the driver
knowledge (perceived and reality)
realizing when you are going backwards
stubbornness
listening to the right people
listening to the wrong people
not listening at all
good part/ bad parts


pat

feel free to add to this list
 

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So Pat if I get this right your saying that,

"Speed Cost ...How Fast do you want to Go" :)sphss:D:D
allow me to revise, if you will

thick wallet - $$$$ + (time)squared = boat speed

a lot of other factors will sway the results
The magnitude of the "man orbs" possessed by the driver
knowledge (perceived and reality)
realizing when you are going backwards
stubbornness
listening to the right people <---- Very Important
listening to the wrong people
not listening at all
good part/ bad parts


pat

feel free to add to this list
 

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Einstien

allow me to revise, if you will

thick wallet - $$$$ + (time)squared = boat speed

a lot of other factors will sway the results
The magnitude of the "man orbs" possessed by the driver
knowledge (perceived and reality)
realizing when you are going backwards
stubbornness
listening to the right people
listening to the wrong people
not listening at all
good part/ bad parts


pat

feel free to add to this list
Einstiens theory of boatativity is as follows: The speed of the boat is directly proportinal to the thickness of the wallet.
Denis
 
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