Your questions re: pump size, hp, speed

[Speedling]

Ok, so obviously I love to go fast. I have tried to do a little tweaking to my engines with what's out there, and made a little progress, but nothing huge.
So people said the pump is the point of limiting factor for it all.
I didn't believe it.
We then watch the 1.8's with 180 hp come out, and be more efficient and faster.
And then the 200 hp superchargers come out, and on a single engine boat the efficiency goes DOWN and we see about the same speeds.
And then you have the Rotax options, of twin 200's and twin 250's that don't go much faster.
AND THEN, you have Berkely, Hamilton, and the like.
So what gives?
I'd love to tell you that I have the answer. And I have got some basic equations figured out, but I have a ways to go in making them accurate in real life.
So what do you guys think are things that need to be considered in all these scenarios?
Here's a list of things I have compared and contrasted between boats/pumps/hulls/engines etc.
Pump size
Horsepower
Torque
Pitch of impeller
Impeller diameter
Number of vanes
Efficiency
Overall water volume coming out of pump
Overall water volume inside of the pump
Surface area of the pump
Rpms of engine and pump
Design of pump and it's optimal characteristics
Weight of the boat in regards to pump loading.
Velocity of water coming out of the boat.

OH! and some things I wondered about...
Do the new Yamaha's have an 8 vane pump? If so, they have the new SVHO pumps which will make a good difference!
And what are the new rotax boats using? The older 155mm pumps from sea doo? Or the newer 159 mm pumps?

I was getting into things like stepped hulls and characteristics of the hull, but kinda stepped away from it due to the fact that there is SO much to look at in regards to researching the engine and pump that I could spend a lifetime.


MMMMMMMMMMMMMMMMk hopefully I get some feedback as I have like 10 pages of research that I'm still sorting through, and a bunch of equations running around.

On another note... one more thing. Anyone know how to make a picture file from an excel spreadsheet graph? Some cool stuff in there I'd love to share when I have it more figured out!

 

[Britboater]

I have an FZR Waverunner and when you WOT you don't really get a "time to plane" it just go's, then hits 70mph in a few seconds. Then we have the SX192 with the same engine, and I'm assuming the same pump, which gets onto the plane in seconds then tops out at around 55mph.
The only real difference then is weight, and surface area, which all makes sense.

Then, when a boat has twin engines, the hole shot can be reduced but you still have a large, heavy object and to push it, and keep it at a high speed, with all the surface drag is very difficult. No doubt it can done but at a cost.

My theory, for what it's worth, is trim. My FZR has the ability to trim the angle of the pump outlet, when I trim the pump to its max I definitely get a higher top end, it makes sense, the nose is high so air gets underneath = less drag. O/B engines have the ability to trim and you get some seriously higher speeds when WOT.
It would be interesting to fit the trim from a Waverunner to a boat to see the difference, but I'm not sure how you would activate it, due to it being a mechanical system. But I have noticed the 2015 top end Waverunners now have an electrical system "Ride" which I'm sure could be fitted to the boats.

 

[Seadeals]

For your excel post, do a screen capture using the print screen button the paste into Paint or some other image program (windows) or if you have it viewable on an iPhone/Pod/Pad, hit the top right and center bottom buttons at the same time to capture the screen.

There definitely seems to be a point of diminishing returns when it comes to speed. I saw an offshore racing boat (advertised as the current fastest v-hull) parked by the fishing hall of fame near FLL last week (Ft. Lauderdale FL). The props always seem to be removed for transit. Thought 1: They treat the props like gold. I suspect even the tiniest flaw destroys performance. Thought 2: take a look at how extreme the design differences are between a standard prop on a runabout and and offshore racing boat. I would expect an impeller for such speeds to be similarly radical.

 

[Speedling]

I have an FZR Waverunner and when you WOT you don't really get a "time to plane" it just go's, then hits 70mph in a few seconds. Then we have the SX192 with the same engine, and I'm assuming the same pump, which gets onto the plane in seconds then tops out at around 55mph.
The only real difference then is weight, and surface area, which all makes sense.

Then, when a boat has twin engines, the hole shot can be reduced but you still have a large, heavy object and to push it, and keep it at a high speed, with all the surface drag is very difficult. No doubt it can done but at a cost.

My theory, for what it's worth, is trim. My FZR has the ability to trim the angle of the pump outlet, when I trim the pump to its max I definitely get a higher top end, it makes sense, the nose is high so air gets underneath = less drag. O/B engines have the ability to trim and you get some seriously higher speeds when WOT.
It would be interesting to fit the trim from a Waverunner to a boat to see the difference, but I'm not sure how you would activate it, due to it being a mechanical system. But I have noticed the 2015 top end Waverunners now have an electrical system "Ride" which I'm sure could be fitted to the boats.

I have a wedge installed on my boat to see if it would make a difference. Slightly slower on plane, slightly higher speed, like 1 mph, and a larger wake and spray out back. What the wedge does is get a little more hull out of the water. What is interesting though is when you hit about 40 mph. It's like the boat settles down and overcomes what the wedge does for putting the bow up.
Surface area etc of the boat is another task altogether and more than i care to take on at the same time.
A good speed hull can give you 5 mph easy. A catamaran hull is good for 10 mph.

 

[Speedling]

Props vs impellers quick look:
Want more speed in a prop boat? Get more power, get a taller prop, done.
Jet boats are more specific. A pump is designed for an optimal amount of rpm and water volume at specific velocities.
Yamaha pumps are optimal at 7000rpm. This is why mr1 engines are reduced. More power, taller impeller equals more water ot the same sized nozzle which is a higher velocity. It is diminishing returns on the horsepower in regards to efficiency (hp vs speed) because the pump can't process the amount of water desired and you are overcoming the resistance with an exponential amount of horsepower.

The prop you show is the next best thing to jets, surface drives! A prop designed to run along the surface and designed to cavitate on purpose!

Thanks for the screenshot tip for the graph!
Keep the ideas coming! I am just making sure i haven't missed something before i send out a big report to you all!

 

[robert843]

Something I see a lot of people do on the 1.8 on waverunners is get the ecu tuned and revlimiter off which has given them a higher rpm running at WOT thus giving them a higher top speed not sure if it would work the same on the boat but it may.

 

[Speedling]

Something I see a lot of people do on the 1.8 on waverunners is get the ecu tuned and revlimiter off which has given them a higher rpm running at WOT thus giving them a higher top speed not sure if it would work the same on the boat but it may.

Yeah, there is very limited things to do with the mr1 engines, and still not a ton for the 1.8's.
This is more interested in the pump design in relation to the horsepower of the engine, whatever the source.
I had started a thread on the old site about just simple top speed type of thing, but while that may be an end goal, I hope that the information I will be providing soon will help all aspects for all jet boat owners.
I am looking for more aspects of the pump I may have overlooked!
The lack of responses means i am probably hitting it pretty well!
And 1.8's need to have a bit of tweaks and such to get them to about 200 hp and I bet these things would be about as optimal as possible. Thing is, that would be putting them above the designed rpm of the pump.

 

[robert843]

Yeah, there is very limited things to do with the mr1 engines, and still not a ton for the 1.8's.
This is more interested in the pump design in relation to the horsepower of the engine, whatever the source.
I had started a thread on the old site about just simple top speed type of thing, but while that may be an end goal, I hope that the information I will be providing soon will help all aspects for all jet boat owners.
I am looking for more aspects of the pump I may have overlooked!
The lack of responses means i am probably hitting it pretty well!
And 1.8's need to have a bit of tweaks and such to get them to about 200 hp and I bet these things would be about as optimal as possible. Thing is, that would be putting them above the designed rpm of the pump.

Yes you are playing with a slippery slope here. Any one of these changes will effect different things. There is no need to upgrade the pump unless you increase the RPM's but even then i have seen negative results from time to time once again this is more from jet ski's never messed with this on the boat just left it stock. One of the main reasons is even in jet ski's with all of these upgrades we are fighting for a few mph at best 5-10mph with no major engine changes anymore it needs to be turbo or super charged. In these boats we would be fighting for 2-5mph at tops and probably not even that with the weight.

 

[scot71]

OK, so here is an idea I would put out there. And please bear in mind that a lot of this seems to be a little over my head.
Increase the OAL of the impeller and increase the amount of twist to each blade (say one full twist per blade rather than the half twist there currently is) and make the pitch progressive. Wouldn't this cause them to act similar to a dual stage pump? The water would be further compressed as it moved thru the progressive pitch of the impeller and I would think this would increase the velocity coming out. This could actually be done relatively easy. It would just involve a different impeller, longer wear ring component, and a longer shaft. My only concern with anything that is done with what already exists is. In order to get more out of the pump, wouldn't there have to be more going into the pump? With the intakes being molded into the hull of the Yamahas and not independent like a Berkeley. Wouldn't an entirely new hull or jet design integrating its own intake have to be designed to allow this? Just a couple cents from my little brain.

 

[Speedling]

OK, so here is an idea I would put out there. And please bear in mind that a lot of this seems to be a little over my head.
Increase the OAL of the impeller and increase the amount of twist to each blade (say one full twist per blade rather than the half twist there currently is) and make the pitch progressive. Wouldn't this cause them to act similar to a dual stage pump? The water would be further compressed as it moved thru the progressive pitch of the impeller and I would think this would increase the velocity coming out. This could actually be done relatively easy. It would just involve a different impeller, longer wear ring component, and a longer shaft. My only concern with anything that is done with what already exists is. In order to get more out of the pump, wouldn't there have to be more going into the pump? With the intakes being molded into the hull of the Yamahas and not independent like a Berkeley. Wouldn't an entirely new hull or jet design integrating its own intake have to be designed to allow this? Just a couple cents from my little brain.

Good point on the intake!
There were a few posts in random forums that I found concerning making the intake SMALLER thus increasing the intake velocity of the water, and therefore allowing for a steeper pitched impeller meaning more speed. This too has only minor tweaking possible with diminishing returns. Instead of cutting up your boat, you can simply make a small plate that blocks off the front or back of the intake therefore making a smaller intake. Or, in one case I researched, they made a "bladder" that expanded out as speed increased making a smaller intake tract.
In any case, I thought about testing that before I came to any conclusions because there really isn't any math that I could find to back that up. Testing is a whole different animal as I have to figure out exactly how to do it!

 

[scot71]

What about instead of blocking the intake to increase the velocity. You necked down the intake to the impeller and went with the steeper pitch. This way you wouldn't decrease the volume going through the pump. I realize this probably can't be accomplished with the current pump, but another idea.

Here's another idea for ya. Variable diameter nozzle. Would help find the sweet spot in varying conditions.

 

[Speedling]

Inteli-jet has a variable intake
Adjust a thrust pump cones essentially make a variable nozzle.
From real world results they both may give more hole shot and then get top speeds where the comparitive pumps would be anyways.
Thing is, these are ways of tweaking current systems. If you took out a mr1 engine and put in the rotax 250 hp engines, where does that put you? 180 hp but subtract 20 hp due to water pump (excessive) so 160 hp extra, and you go from 50 to 60 mph. Below the supercharger realms it seems that every 10hp means one mph. This means that the 500 hp boats should be 66 mph. They aren't. After a certain point for a pump size any type of tweaking will be met with continuous diminishing returns.

 

[scot71]

After a certain point for a pump size any type of tweaking will be met with continuous diminishing returns.

You're exactly right. If these pumps are working at thier peak efficiency, adding more power is not going to make an appreciable difference in performance. You also have to remember that or very mph that you go faster. The forces working against the boat are multiplied i.e. wind resistance,water resistance, etc.. That is part of the reason, for example, why a top fuel dragster has to run 10,000 hp and look the way they do to overcome these forces and run 300+ mph. I would venture a guess that from just a wind resistance standpoint. A boat without a tower would be ever so slightly faster than one with a tower. More than likely only tenths of a mph, but still faster. The only way that I can see that a large jump in speed can be achieved is by changing the pump. As hp increases (increased velocity), pump size must increase (volume of water). The sad part is as boat size increases. The hp and pump size must increase as well. Just to keep pace with the smaller package. Eventually you end up with something like this.

 

[Speedling]

I'll take two!

 

[davel501]

I have noticed weight distribution makes a difference as well. Having a decent amount of weight, like say even an extra 100-150 lbs in the bow will slow the boat down a few mph.

 

[txav8r]

You're exactly right. If these pumps are working at thier peak efficiency, adding more power is not going to make an appreciable difference in performance. You also have to remember that or very mph that you go faster. The forces working against the boat are multiplied i.e. wind resistance,water resistance, etc.. That is part of the reason, for example, why a top fuel dragster has to run 10,000 hp and look the way they do to overcome these forces and run 300+ mph. I would venture a guess that from just a wind resistance standpoint. A boat without a tower would be ever so slightly faster than one with a tower. More than likely only tenths of a mph, but still faster. The only way that I can see that a large jump in speed can be achieved is by changing the pump. As hp increases (increased velocity), pump size must increase (volume of water). The sad part is as boat size increases. The hp and pump size must increase as well. Just to keep pace with the smaller package. Eventually you end up with something like this. View attachment 14589

Did you notice? Pat Sajak has a second job!

 

[scot71]

Did you notice? Pat Sajak has a second job!

Holy Crap! That's some funny stuff right there!

 

[scot71]

I have noticed weight distribution makes a difference as well. Having a decent amount of weight, like say even an extra 100-150 lbs in the bow will slow the boat down a few mph.

That makes sense to me. Having more weight in the bow I think would make it ride lower thus having more of the hull in the water. Causing much more drag in the water.

 

[Speedling]

That makes sense to me. Having more weight in the bow I think would make it ride lower thus having more of the hull in the water. Causing much more drag in the water.

Correct.
Something else to think about: the same engines and pumps in different boats still creat the same amount of thrust. One may be heavier and have more hull in the water and with the same application of thrust they will go different speeds. This doesn't cause cavitation at all in ajet pump. In fact, you could tie to a tree and produce the same amount of thrust. You just won't go anywhere.
This is why people tend to think of jets as being so torquey. Jets can be put to full throttle, creating max thrust, and the boat catches up.

 

[scot71]

Jets can be put to full throttle, creating max thrust, and the boat catches up.

That's one of my favorite things about these boats, instant power.