What is the theory behind minimum speed for nosecones?

[Riverman]

Of all the reading I have done on here (it's a lot!) I have yet to find a discussion on why there is a minimum speed for nosecone use. What I have read seems to conclude that a nosecone is actually detrimental to top speed below around 70-75 MPH. If one anticipates a top speed of around there, that's a pretty pointy fence to have to sit on. I'd like some opinions on this one way or another, and some hard theory on the subject if it's out there.

Thanks :)

[StratosVT]

The nosecone case is slower because it is longer. The extra length makes it less hydrodynamic. However, a noseconed case will allow you to run the motor higher (and still get h20 pressure). A higher case runs in less water, experiences less resistance and therefore will allow a motor to turn higher rpm than a lower running gearcase. In a nutshell, if you were to run a noseconed case at the same height as you run a regular case, it'll be slower. When you raise the height (nosecone case) it can give you better performance if you have the right setup and hp/weight ratio to make up for it being less hydrodynamic.

[pyro]

Aslo, most sub-70 mph boats need some positive trim to reach their 60-70 mph top end, instead of using aerodynamic lift as most boats would ABOVE those speeds. Nosecones don't like lots of positive trim, it tends to add tond of drag if there's water flowing over the top of a nosecone that's excessively trimmed.

Nosecones also lengthen the gearcase bullet to raise blowout speed, of course. Non-coned gearcase blow out in the low 80's on most boats, and coned cases are often slower below 70 mph on the same hull.

[neveredge]

I put a land and sea nose cone on my GT175 on my Ranger 361V. I did not gain any speed at all, but I did not lose any either. The nosecone also made the boat much easier to drive at WOT.

This boat ran a best speed of 72 mph but with a normal fishing load it would run about 65. 67 with my wife instead of my buddy, she weighs less.

The 72 mph is a radar speed. The 65 and 67 are speedo speed. On the 72 mph run the speedo showed 70 mph so I think these figures are fairly accurate. Fishing prop was a 27" shooter at 5850 RPM. The speed prop was a 28" hoss triton over hub chopper at the same rpm. The nosecone didn't change any of the speeds.

[dlivewyer]

The longer more pointed nose tightens up the water flow around the l/u thus reducing the amount of air mixed with the water going to the prop. The tighter flow of water increase the drag, but also makes it drive better.

[wideglide55]

I'd say if you are gonna run 70-75 that a cone is a good idea from a safety standpoint, especially on a v-pad hull,tunnels like mine are more forgiving in a prop blowout situation.

[wideglide55]

I've seen v-hulls switch ends when the prop let go.

[Riverman]

Thanks everyone for the good info. I already bought a LWP from Mazco and didn't know whether to install it or not. I'm going to stitch weld it in place and then blend the surfaces with epoxy.