Performance Boats Forum banner

1 - 20 of 74 Posts

·
Registered
Joined
·
4,045 Posts
Discussion Starter #1
What is best HP or Torque? Lets say I have a motor that makes 650 HP @ 5700 RPM and also 650 HP @ 6200 slight loss in HP between 57 - 62. But at 5700 torque is 640 and at 6200 it is 610 what RPM would I want the jet to turn for best performance?:)Unsure
 

·
Registered
Joined
·
4,045 Posts
Discussion Starter #8
LMAO! You guys take the cake! but, it still leaves the question of RPM for the pump!:D
 

·
Banned
Joined
·
1,263 Posts
What is best HP or Torque? Lets say I have a motor that makes 650 HP @ 5700 RPM and also 650 HP @ 6200 slight loss in HP between 57 - 62. Unsure
You have a hp dip between 5700 and 6200 ?

What's your peak tq and what rpm ?
What's your peak hp and what rpm ?

Do you have a dyno sheet to show someone so they can help ?
Can you give more details on the boat also ?

BTW: I'm no jet boat guy, therefore I'm asking engine 'tune' questions and and other questions that may help others help you.

Oh, and 6200 will sound faster than 5700. :)hand (joke)
 

·
Resident Ford Nut
Joined
·
10,075 Posts
What is best HP or Torque? Lets say I have a motor that makes 650 HP @ 5700 RPM and also 650 HP @ 6200 slight loss in HP between 57 - 62. But at 5700 torque is 640 and at 6200 it is 610 what RPM would I want the jet to turn for best performance?:)Unsure
I love this question, it will not be easily answered. What are the observed HP #'s. I'm assuming the posted numbers are corrected ones.

Off the top of my head I would guess an slightly worked Berkley A/B cut will put you at about 6,000 rpm's. I would start with that... Now if you go for a fully worked over race pump it could be as small as a B/C cut.

You'll get about 15 different opinion's on this... Thanks for the entertainment.

There is an Impeller chart posted here somewhere. If someone else doesn't post it I'll find it. Actually there are two charts.
Edit:


Also, do you have this engine or is this hypothetical ?

Sleeper CP
Big Inch Ford Lover :D
 

·
B.A.M aka "Black Azz Mike
Joined
·
2,925 Posts
This is one of the most debated topics I have been viewing since 2000;)

This thread should get pretty damn good...................
 

·
E-7 Sheepdog (ret)
Joined
·
6,834 Posts
What is best HP or Torque? Lets say I have a motor that makes 650 HP @ 5700 RPM and also 650 HP @ 6200 slight loss in HP between 57 - 62. But at 5700 torque is 640 and at 6200 it is 610 what RPM would I want the jet to turn for best performance?:)Unsure
Depends.

Depends on what RPM you want to twist the engine to.
Depends on what impeller cut you want to run.
Depends on what youy want to use the boat for.
Depends on how you want to define "performance", BY INTENDED USAGE.

"Performance" for a 1/4 mile drag jet is nowhere near the same as "performance" for a lake boat that pulls people on tubes/skiis all day and carries 5 people to fireworks shows 5 miles down-lake in the evening and then back.

Generally, larger impellers reduce RPM (thus engine wear and fuel consumption), increase acceleration (holeshot) and increase pulling ability (skiis/tubes).

Conversely, Generally, smaller impellers make slightly more top speed, at a loss of acceleration and pulling ability, and require higher RPM.

Torque is the only thing an engine generates anyhow, "twisting force by the crankshaft" is TORQUE.

All Horsepower is is a mathematical calculation of torque generated over time.
 

·
E-7 Sheepdog (ret)
Joined
·
6,834 Posts
This is one of the most debated topics I have been viewing since 2000;)

This thread should get pretty damn good...................
Yea, it is 396, and I will most likely be lurking for the rest of the fight. :D
 

·
Sit N' Spin
Joined
·
1,423 Posts
Does the engine/pump know what boat it is in?
To answer this...no they don't. The engine just spins the pump, the pump allows the engine to swing up to a certain max RPM depending on how well the pump loads, engine HP curve, etc etc. X amount of thrust is made...and that's where thrust/weight ratio comes in.

Honestly..the whole "heavy boats like torque, lighter boats like HP"...if you have a motor with enough torque to shoot a heavier boat out of the hole like a rocket and you put that same motor with the same pump in a lighter boat, I would think it would do even better in the lighter boat due to less weight.

But the one point nobody can argue with...jet boats definitely prefer Chevy over Ford :D :D :D
 

·
E-7 Sheepdog (ret)
Joined
·
6,834 Posts
But the one point nobody can argue with...jet boats definitely prefer Chevy over Ford :D :D :D
There's the 55 gal barrel of gasoline. Who's got the torch?:D:D:D
 

·
Registered
Joined
·
288 Posts
ive been told that torque is what gets ya goin and HP is what makes ya fast. So what you need to do is figure out where your running and ask the pump guru's.:|err
 

·
E-7 Sheepdog (ret)
Joined
·
6,834 Posts

·
E-7 Sheepdog (ret)
Joined
·
6,834 Posts
1 - 20 of 74 Posts
Top