Lets talk cruising speeds..

[396_WAYS_TO_SPIT]

Lets say that you had 400hp @ 4000 rpms. Where would you be running on the GPS? WHat about 500hp@4000 rpms? :idea: :idea:
Oh and of course this would be in a medium layup(500-600lbs) hull with a tight pump;)

[cyclone]

What type of hull and what size impeller?

[396_WAYS_TO_SPIT]

um........
19ft tunnel(ie daytona,ultra,cheyenne)
18 or 19ft gullwing
18ft v bottom
"A" impeller
"A/B" impeller
"B" impeller

[Duane HTP]

What ever speed you run with 400 hp @ 4000 rpm would be exactly the same speed that you would run with 500 hp at 4000 RPM. RPM is the determining factor, not HP. Now if you changed impeller sizes between the two there would be a difference. The 500 HP motor might pull a larger impeller 4000 rpm which should relate to more speed in the same boat. But to just take the two motors to 4000 rpm with the exact set up and impeller size, there would be no difference.

[396_WAYS_TO_SPIT]

Aww I see.
Ok lets play with a few numbers.....
Lets say that if you run 95mph @ 6200r's then where would you be @ 5000/4500/4000 r's?

[DMOORE]

I'm not an expert on jets, but with a prop, rpm's do not corralate to speed in a linear fashion like a car does. This is due to prop slip.On a high performance prop set up ,the prop will become more efficient at the higher speeds. In a car for example 3000rpm=50mph.so, 6000rpm's would =100mph. I have a feeling a jet will have a certain point where the pump is at it's maximum efficiency. (obviously impeller related). Interesting to hear from someone in the know.
Darrell.

[MudPumper]

It all depends on what the speed of the treadmill is set to. :D

[MudPumper]

What type of hull and what size impeller?
Why haven't you hit the road yet????

[396_WAYS_TO_SPIT]

It all depends on what the speed of the treadmill is set to. :D
Aw hell, here we go again :D Mikes chillin' with the clown suit on tonight:D How have ya been brotha?

[MikeF]

Aww I see.
Ok lets play with a few numbers.....
Lets say that if you run 95mph @ 6200r's then where would you be @ 5000/4500/4000 r's?
Approx........77/67/57 mph....... For a typical well performing Vbottom hull.:)

[396_WAYS_TO_SPIT]

Approx........77/67/57 mph....... For a typical well performing Vbottom hull.:)
Thats doesn't sound too shabby. Could you please elaborate for us....

[cyclone]

Why haven't you hit the road yet????
i figured i'd make a grand entrance......:D

[MudPumper]

Aw hell, here we go again :D Mikes chillin' with the clown suit on tonight:D How have ya been brotha?
Don't have the suite on but I am wearing the big shoes and the red nose. :D I'm good, itchin to hit the river though. Saw some boats headed out this afternoon and made me jealous as hell.

[MudPumper]

i figured i'd make a grand entrance......:D
Thought registration was at 7pm at the Arroweed. Hope they allow late entries. :D

[pw_Tony]

What about 550 lbs of torque at 4500? Is there a difference betwwen horsepower at that RPM and torque?

[MikeF]

Thats doesn't sound too shabby. Could you please elaborate for us....
When I had tested my boat, that's the #'s I came up with. 10mph for every 500rpm. Once the boat is on plane, the speed vs' rpm is very linear......until you get into higher speeds (in which the air is now helping lift the boat).
What about 550 lbs of torque at 4500? Is there a difference betwwen horsepower at that RPM and torque?
Spinning an impeller a certain speed is what is relevant. But the more torque you have, the more rpm you should be able to turn (= more HP as rpm goes up).

[396_WAYS_TO_SPIT]

When I had tested my boat, that's the #'s I came up with. 10mph for every 500rpm. Once the boat is on plane, the speed vs' rpm is very linear......until you get into higher speeds (in which the air is now helping lift the boat)..
Thats what I was looking for;) Thanks Mike;)

[71tahiti]

I have a AA berk in an 71 18' tahiti torino(wide beam) w/455. I thought AA pushed more water at the same RPM?? 13 yrs ago old guy (bob i think) at Berkeley told me "I should run AA in Olds". I understand the typical limits of my olds(rpm,oiling,) and figured thats why he said that. Is it individual to the engine built as to which impeller is best? I have mildly built 455 w/tach only. 4400 rpm with AA. My Buddy said I was running 57 but I have since replaced a soaked floor and dug out GOBS of SOAKED FOAM!!!!!
If I stay with the Olds and rebuild should I stay with the AA? Which is faster 4800-5000 with olds and AA OR an A,B,ect.. @5500 with BBC?

[ck7684]

I'm no expert, so dont take my word for it, but isnt a smaller impeller better for a higher operating RPM?? Larger impeller better for low down?? Seems to me that a larger impeller would pump more water, but take more horsepower to turn at a higher RPM...

[77charger]

Aww I see.
Ok lets play with a few numbers.....
Lets say that if you run 95mph @ 6200r's then where would you be @ 5000/4500/4000 r's?
mike only 6200 you know it aint good til you hit 8500 plus and pull to 9500.:D
i'd say at 4k you will be scootin along pretty well.defintely over 50 now can that lil jet handle to water to cruise at 50 plus????
it think is real lake conditions you will be around 2-3k rpm range movin along pretty well and barely workin a motor.

[GUGS102]

I think with my AB. I am running around 33-35 at 3500, 42-45ish at 4000, 55ish at 4500 and 78 at 5200. I can barely hold plane at 2800
It is not until I get the lead out until the boat will take a decent set and get the heavy nose out of the water. Hence the non linear acceleration. This is for a heavy semi V hallett. Even at WOT I am still breaking water in front of the motor about half way up the back seat.