Intake Pressure

[Instigator]

This year the pump is going to be fine tuned. Want to install a pressure gauge for my intake pressure and bowl pressure. Where is a good location to drill and tap these parts for fittings? And I know this will be a can o worms, but anybody got any guidelines for intake pressures? I assume you want the lowest intake pressure possible while still maintaining bowl pressure? What I am after is making sure I'm not biting too much water and slowing the boat down. V-bottom jet, 75-80 mph.

[Rondane]

This year the pump is going to be fine tuned. Want to install a pressure gauge for my intake pressure and bowl pressure. Where is a good location to drill and tap these parts for fittings? And I know this will be a can o worms, but anybody got any guidelines for intake pressures? I assume you want the lowest intake pressure possible while still maintaining bowl pressure? What I am after is making sure I'm not biting too much water and slowing the boat down. V-bottom jet, 75-80 mph.
Either at 10 clock or 2 oclock on the suction about 1 inch infront of the wear ring surface is about the best area. Make sure you pressure guage is steady at all times without fluctuation and about 35 to 40lbs to start.
rondane

[centerhill condor]

the true measure of your pump's efficiency is differential pressure... or Dp... which is the energy the pump ads to the flow. you can either have two pressure gauges and subtract or connect the inlet to the outlet and have one pressure measuring device. you will lose a small amount of thrust due to the return flow rate. However, if you make the return line out of 1/4" tubing the amount will be neglible. as for what to expect, you can find a pump performance curve somewhere on the net as your jet drive is a pump... axial flow. In any event, when measuring pressure... ad 14.696 psi to convert to absolute pressure from psig (gauge pressure). don't forget to ad the energy required to raise the flow from the bottom of the boat to the centerline of the jet's nozzle. It may not appear to be very much. but at 4,000 gpm it does make a difference in your calculations. but you probably already knew that.
when you get your Dp data at different rpm (and corresponding hp/torque) and fuel flow, you can then caculate the efficiency of each part and then the entire system. Or I'm sure that one of the other guys can tell you what the numbers should be and go on with life without a slide rule...
I'm interested in your data... jet manufacturers are always touting the efficiency of the jet drive versus props, etc...
good question btw!

[Instigator]

We be gettin a bit too technical there. I appreciate the input, but I'm trying to keep it simple. More along the lines of --- intake pressure is or course near nill at idle speed, I've heard of 10,15,30lbs, ect at WOT. Bowl pressure's what-----80-100lbs? (at WOT) Of course that depends on the hp the motor puts out---- right? Too much shoe or too much loader bite, can slow you down, right?

[GTBOATS]

Bowl Presure Is Not As Important As The Speed And Thrust Out Of The Nozzle. A Lot Of Things Can Raise Bowl Pres. And Not Change Speed. Suction Pres. Can Also Give A The Tail Of The Boat Lift.

[jweeks123]

Either at 10 clock or 2 oclock on the suction about 1 inch infront of the wear ring surface is about the best area.could you explain why that is the best area
jw

[steelcomp]

could you explain why that is the best area
jwI was going to ask the same question.

[Aluminum Squirt]

I have no comment on the best area but from what I understand, its all relative. It's impossible to get the same numbers from two different boats even if you measure and drill very carefully in the same spot. Mount it where one of the smart guys tell you and get numbers, those numbers will be your numbers and not very comparable to anybody else. Use them to tune, who cares if they are "what they should be." Get some numbers, make a change and see what happens on the GPS-Aluminum Squirt

[Cs19]

I was thinking along the lines of 20-40 lbs. on the inlet and 200 on the bowl (not droop) for a mild hotrod lake boat??? I never seen data on something like that so its hard to say.If you can get 50 on the inlet, go for it. On the bowl, the higher the better.
I agree with Jak when he says not to get too high on the inlet.The jet can only process so much water, now people like to say that really high inlets create lift and thats a whole different subject that probably wont get talked about here. .
Whats frys my unit is I started a thread about inlet pressure a while back and the thread tottally sucked. I was prepard to discuss everything in detail and go over my numbers Ive gotten from my data logger but none of the techie guys took the bait.A guy with a set of guages from pep boys got more replys that I did.
Im starting to believe that racer chit LVjet talks about is true.

[dragboat]

I was thinking along the lines of 20-40 lbs. on the inlet and 200 on the bowl (not droop) for a mild hotrod lake boat??? I never seen data on something like that so its hard to say.If you can get 50 on the inlet, go for it. On the bowl, the higher the better.
I agree with Jak when he says not to get too high on the inlet.The jet can only process so much water, now people like to say that really high inlets create lift and thats a whole different subject that probably wont get talked about here. .
Whats amazing is I started a thread about inlet pressure a while back and the thread tottally sucked. I was prepard to discuss everything in detail and go over my numbers Ive gotten from my data logger but none of the techie guys took the bait.A guy with a set of guages from pep boys got more replys that I did.
Im starting to believe that racer chit LVjet talks about is true.
You've got the floor, now spill it