Horse power or torque?

[craigman]

Don't know if this is the correct forum to post in, but i'll try anyways.
I was wondering what is more important for jet boat? Horse power or torque?
A little info, i've got a 23 day cruiser powered by a 460 Ford and a Berkely jet.
Just wanting to know for a future engine build.
Thanks for any info!
Craig

 

[Scott Danforth]

Re: Horse power or torque?

Horsepower=torque X RPM / 5252

you cant have horsepower without torque.

now, you can spin an engine faster with a fixed torque you get more horsepower.

if your looking to add power to the engine, it wont matter too much unless you modify the jet (impeller and nozzle) to make use of the new power.

 

[QC]

Re: Horse power or torque?

Unless you are building for dry stacks then it is kind of a moot point anyway. Do some reading on "reversion". Generally speaking though, unless she struggles to plane, you build for horsepower. The odd thing about reversion is you kind of end up with a lower speed, high torque, setup anyway. Jets are know for hole shot, so increasing low end torque is probably even less beneficial to a jet as that's what you get with high torque, better hole shot. The point being that jets help compensate for poor hole shot, so the benefits of good low end torque may be lessened. My guess is light hull, and that you want higher speeds. I'd build a 5000ish RPM, high horsepower setup and work on my impeller specs to match.

 

[craigman]

Re: Horse power or torque?

Thanks QC. I'm not running dry stacks so i'll do some searching on "reversion".
Scott, i'll look into the jet for better performance.

 

[craigman]

Re: Horse power or torque?

Looks like with a thru the transom/wet exhaust i'm pretty limited on hp/tq.

 

[QC]

Re: Horse power or torque?

Tell us more about your boat and expectations. What are you trying to do? I have some jet experience in my past as they were popular on the Colorado river.

 

[craigman]

Re: Horse power or torque?

QC,
i'm just on the quest for more speed like everyone else! LOL!!
I'm new to the jet boat world. I'm going from my little 15' outboard (32mph max!) to a 23' day cruiser with a 460 and a jet.
Like I said, i'm just looking for info for a future build. I know V drives, I/O's, ect. look for max hp. and rpm's. I know nothing about jets so that's the reason I was asking about hp. vs tq
I've heard that when jets get to a certain rpm they start to cavitate. Don't know if this is true or not. Like i said, i'm still learning about jets.

 

[QC]

Re: Horse power or torque?

That sounds like a 50 MPH setup. Have you run her yet? Sea level? What hull? Pump?

 

[craigman]

Re: Horse power or torque?

No I haven't ran her yet. I've got some floor replacement and paint work to do first.
I'm just assuming it's a 40-45mph boat.
It's a 1979 23' Carlson/Glastron day cruiser with a Ford 460 and Berkely 12J pump. (i think) It's wieghs 1400lbs. empty.
And i'm at 600' above sea level.

 

[Jlawsen]

Re: Horse power or torque?

Your 460 is a good candiate for your boat but that 12Jc is mediocre at best when it's stock. You can make them a lot better but you'd see a lot more performance out of a two stage Scott. It's got a hefty price tag but it will get you out of that 30% efficiency loss of the Berkeley. I ran modified Hamiltons for their beef until I found the Scotts. Just google Scott Waterjets, they're out of New Zealand where the sport is finely honed. Not sure where you are but in the states the guys to talk to are Jet Stream Concepts in Yuba City, Ca. Phil Taylor is the guy you want to talk to. QC's advice has you on the right track, Phil can help you nail it. Buy the pump from him and you'll be amazed what he'll teach you.

 

[craigman]

Re: Horse power or torque?

I'm actually 3 hours north of Yuba City!

 

[QC]

Re: Horse power or torque?

It's a 1979 23' Carlson/Glastron day cruiser

Waaay cool. Got any pictures?

 

[craigman]

Re: Horse power or torque?

QC,
It's nothing fancy right now. Like most older boats it needs some floor work, upholstery, and some paint work. Lucky for me i'm a body/paint tech so I can take care of most of it!. But i'm pretty happy with it. Escpecially for a low low price tag of $500! And it runs!