HP or TORQUE

[LeadFootTheRabbit]

I think it's CUBIC DOLLARS x RPM's (rich persons money) that makes your boat fast. My pappy always said "Speed Costs Money, how fast do you want to go".
LDFTRBT

[Clown]

mikey-jones:
so correct me if i am wrong
high RPM and the right impeller determine your top speed , horsepower determines your higher RPM. and torque gets you goin. something like that? I think you got it! There are charts out there that will get you in the ball park to figure your HP
Its what rpm you can turn to what what impellior====
Your HP It gets you real dang close!

[Infomaniac]

The RPM that you intend to turn your engine should determine whether you build for Torque or Horsepower.
If you plan to run your engine less than approx. 6,000 RPM, build for torque.
Any more than 6,000 RPM start looking at HP components.
I have pointed out this fact on numerous occations: All engines make more torque than HP below 5,252 RPM, and more HP above 5,252 RPM. But HP and Torque are equal at that RPM.
To build an engine that makes more HP than torque, it will require some big RPM's (or a blower/nitrous)
If you build a jet boat engine that makes big HP, make sure the RPM's accelerate up there quick. wink
[ September 22, 2002, 08:46 AM: Message edited by: Infomaniac ]

[mikey-jones]

So what does it take to add torque to your motor? if my motor makes 350 hp and 490 lbs of torue right now what would a 100 shot of nos do for it. Hp and Torque wise.

[Infomaniac]

mikey-jones:
So what does it take to add torque to your motor? if my motor makes 350 hp and 490 lbs of torue right now what would a 100 shot of nos do for it. Hp and Torque wise.That is a innocent sounding but very complex question. What RPM do you run wide open? Adding torque is not necessairily the answer. If you operate your engine in the torque range instead of the HP range. Flattening out the torque curve should be the goal. Peak torque is not the objective. To have the most amount or torque for the widest RPM range will be the best in that situation. The engine will have to be built specifically for that.
Adding a small shot of NOS will give you some more RPM's which should increase your speed. How Much? Anyone's guess. If it puts your engine into an RPM range that makes more power than what it runs now, it will benefit more. To answer your question specifically. It should increase both HP and Torque.

[mikey-jones]

i am currently running around 55 - 60 mph and revving around 4600 - 4800 rpm at WOT i been told this motor should handle 5200 - 5500 rpm. so maybe a ball park figure of how much rpm and top speed i would pick up with a 100 shot or maybe even 150 shot of nos, whatever a big block ford could handle

[HighRoller]

I think the one most important variables are ones left out in this discussion.Boat size/shape/weight and thrust volume vs.thrust velocity.A heavier/bigger boat needs more thrust volume and more torque due to more drag.A lighter boat can take advantage of a higher HP/higher RPM engine because they have less drag and weight and don't need low end torque to accelerate.Also you can"sleeve"the pump in a small boat because increased thrust velocity will help top end.I'm no genius on this topic but I've seen too many guys try to put drag race type engines in full size daycruisers instead of looking for more torque.

[mikey-jones]

the boat is a 1970 16 foot tahiti schuster as for weight i dont know exactly but im sure its not to heavy only took 3 of us to flip it upside down in the garage

[LVjetboy]

That's easy Mikey. Assuming you're running a Berkely A impeller (on a good pump loaded properly) at 4700, 100 shot will give you 5140 rpm and 150 shot will give you 5330 rpm. Other impellers will be somewhat different, but if you know your impeller those numbers can run through JPC too.
Assuming your hull's in good shape the 100 shot will get you near 67 mph and the 150 shot near 70 mph.
Compliments of the JPC.
jer

[77charger]

mikey-jones:
i am currently running around 55 - 60 mph and revving around 4600 - 4800 rpm at WOT i been told this motor should handle 5200 - 5500 rpm. so maybe a ball park figure of how much rpm and top speed i would pick up with a 100 shot or maybe even 150 shot of nos, whatever a big block ford could handlea 100 shot will bring you to around 5k-5200 and about 5-7 in mph